US20040187979A1

US20040187979A1 - Cutting tool body having tungsten disulfide coating and method for accomplishing same

Info

Publication number: US20040187979A1
Application number: US10/403,832
Authority: US
Inventors: Craig LeClaire
Original assignee: Material Technologies Inc
Current assignee: Material Technologies Inc
Priority date: 2003-03-31
Filing date: 2003-03-31
Publication date: 2004-09-30
Also published as: WO2004092429A2; WO2004092429A3

Abstract

A method of manufacturing a tool body of a cutting tool comprises mechanically shaping the tool body to provide a metal surface on the tool body having a first surface characteristic. Thereafter, the metal surface is chemically treated with a metal reactant to create a relatively soft metal film along the metal surface. This soft metal film is removed via burnishing or other appropriate action to smooth the metal surface. After the surface is smoothed, the metal surface is then roughened to prepare the surface for the receipt of tungsten disulfide. The roughened metal surface is coated with tungsten disulfide. A cutting tool is disclosed that comprises a tool body defining a substantially isotropic surface having pits formed therein, and tungsten disulfide particles filled into the pits.

Description

FIELD OF THE INVENTION

This invention pertains to cutting tools and more particularly to surface treatments of cutting tools.

BACKGROUND OF THE INVENTION

Cutting tools such as drills, taps, reamers, milling tools, broaches, etc. are used to drill, machine, mill, ream, hone or otherwise cut stock material into desired shapes. Such stock materials for workpieces include steel of various types and hardness, aluminum materials, and a wide variety other metal and non-metal materials. One of the requirements of any cutting tool is that it typically needs to be harder than the workpiece being cut. Therefore, harder materials such as high speed steel, carbide and diamond are often the materials of choice used for cutting tools. Another requirement is that it needs to have sharp cutting edges. Sharp cutting edges are often accomplished with grinding to provide sharpness for the desired cutting action. Usually, the cutting tools will have flutes to provide a means to evacuate cut chips as they are generated at the cutting edges of the tool.

There are three different basic categories of cutting tools, including (1) solid material tools; (2) brazed on carbide tools; and (3) indexable tools. Solid material tools are manufactured from one material such as high speed steel or solid carbide. Brazed on carbide tools comprise solid carbide “cutters” that are brazed onto a tool body of a different material, often steel, and typically, but not limited to 4140, 4340, H-13 or S-7. Indexable tools comprise a tool body that comprises one material, typically 4140, 4340, H-13 or S-7, and inserts (also known as “cutters”) that are usually made of a different material such as carbide. The inserts or cutters are attached to the cutter body and held in place usually with screws. With screws, the cutter inserts are removable such that they can be indexed to provide a different cutting edge and/or removed and replaced at the appropriate time.

Carbide material is frequently the material of choice for cutting tool edges because carbide is less expensive and easier to use than diamond. Also, carbide is much harder and much more durable than steel, which provides for a much longer tool life. However, carbide costs substantially more than steel material such that solid carbide cutting tools are much more expensive than solid steel tools. As a result, a combination of materials is frequently used, such that carbide cutting tools often comprise a base tool body comprised of less expensive softer steel material and the harder carbide material is confined to the cutting edges.

In all cutting tools, the cutting edges typically carry the largest loads and incur the brunt of direct impact loads. In brazed-on carbide and indexable carbide cutting tools, the hardness of the carbide at the cutting edge therefore vastly extends tool life over conventional solid steel tools. However, in these cutting tools, the softer steel tool body can often be a separate source of problems and can greatly limit tool life as compared with more expensive solid carbide tools. For example, wear and erosion can occur on the surface of tool body, surface galling can occur on the contact diameter of the tool as well as the flutes. Tool body wear can occur behind the cutting edge as result of chip engagement. Among other things, these problems can cause poor chip evacuation and chip packing (and thus increased loads), and can also limit coolant flow. The inability to quickly evacuate chips and insufficient coolant flow can limit tool cutting speed. It is recognized that the ultimate failure with a tool is excessive heat generation. Excessive heat can result from one or more of the issues above.

The common prior art attempts at solving these problems has focused upon three different variables, cutter geometry, flute geometry, and surface hardness of the steel tool body. The cutter geometry can be modified to alter chip geometry for easier evacuation and to prevent galling. Similarly, the flute geometry can be optimized. However, the optimization of these variables provides only achieves limited benefits.

Another common technique that is sometimes employed to attempt to extend cutting tool life is to harden the steel tool body with a hardening operation which is accomplished with heat treatment. Typical approaches include a hardening operation of the entire tool body or surface hardening techniques such as carburizing, nitriding and surface flame or induction hardening processes. These heat treatments typically improve tool body hardness which in turn increases durability and wear resistance. However, these operations can add significant extra expense. Further, exposing the cutting tool to heat treatment can relieve internal tool stress that are created inherently when the tool was originally machined, ground and/or milled, that in turn can cause a slight warping or distortion in the tool. Such distortion or warping can cause an unbalanced loading across the cutting tool during cutting operations which can also lead to premature failure.

BRIEF SUMMARY OF THE INVENTION

The invention provides an improved tungsten disulfide surface treatment on cutting tool bodies and method that can provide for much extended cutting tool life and/or increased cutting speeds, and that substantially reduces the problems associated with surface galling, poor chip evacuation and tool body erosion.

According to an embodiment of the invention, a method of manufacturing a tool body of a cutting tool comprises mechanically shaping the tool body of the cutting tool to provide a metal surface on the tool body having a first surface characteristic. Thereafter, the entire metal surface or selected portion of the metal surface is chemically treated with a metal reactant to create a relatively soft metal film along the metal surface that is removed via burnishing or other appropriate action to smooth the metal surface to a smoother surface characteristic. After the surface is smoothed, the metal surface is then roughened to prepare the surface for the receipt of tungsten disulfide. The roughened metal surface is coated with tungsten disulfide.

A preferred embodiment of a cutting tool that may be produced by this process or other suitable process comprises a tool body defining a substantially isotropic surface having pits formed therein, and tungsten disulfide particles filled into the pits.

Other aspects, objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1, 1[0012] a, 1 b, 1 c, and 1 d are schematic representations, shown in sequence, of a method used to provide a tungsten disulfide coated surface on a metal surface of a cutting tool body, in accordance with a preferred embodiment of the present invention.
FIGS. 2, 2[0013] a, 2 b, 2 c and 2 d are schematic representations, shown in sequence, of the metal surface of the cutting tool body after different stages of the method illustrated in FIGS. 1, 1a, 1 b, 1 c, and 1 d have been accomplished, respectively. Importantly, FIGS. 2, 2a, 2 b, 2 c and 2 d do not depict true cross sections and do not represent accurately dimensional characteristics, but are presented to illustrate and convey the concepts and methods disclosed herein to generate a greater understanding and appreciation of the present invention.
FIG. 3 is a picture of a microscopic SEM image at 300 power of the surface of a sample laboratory mount of a chromium/molybdenum alloy common referred to as 4140 material, hardened and tempered to 30 HRC, having a metal surface that has been subjected to a mechanical shaping operation, leaving a directional finish on the metal surface. [0014]
FIG. 4 is a picture of a microscopic SEM image at 300 power of the surface of the sample laboratory mount similar to that shown in FIG. 3 after a REM® FERROMIL® chemical smoothing process has been applied subsequent to the mechanical shaping operation. [0015]
FIG. 5 is a picture of a microscopic SEM image at 300 power of the surface of the sample laboratory mount similar to that shown in FIGS. 3 and 4 after the laboratory mount was subjected to a blasting operation with 1200 grit size blast aluminum oxide media at an operational stage subsequent to the REM® FERROMIL® process to roughen the surface of the sample laboratory mount. [0016]
FIG. 6 is a picture of a microscopic SEM image at 300 power of the surface of the sample laboratory mount similar to that shown in FIGS. 3-5, after the sample laboratory mount was subjected to a high velocity impingement of tungsten disulfide particles at an operation stage subsequent to the blasting operation.[0017]

DETAILED DESCRIPTION OF THE INVENTION

The following examples and attached figures disclosed herein further illustrate the invention but, of course, should not be construed as in any way limiting its scope. [0018]
For purposes of illustration, a preferred embodiment of the present invention is illustrated and described in association with an indexable cutting tool and more specifically an [0019] indexable drill bit 10 having a steel tool body 12 and carbide cutter inserts 14 as shown in FIG. 1. The cutter inserts 14 are adapted to be mounted to the tool body 12 with screws 16. As is conventional, the tool body 12 includes flutes 18 that extend axially along the tool body 12 to facilitate chip removal. The tool body 12 may also include coolant passageways 20 in some applications to communicate coolant to the cutting edges of the inserts 14. Although a drill bit is shown, it will be appreciated that the invention is applicable to all cutting tools including taps, reamers, milling tools, broaches, etc. and other appropriate cutting tools.
The [0020] tool body 12 is mechanically shaped through a conventional milling operation 17 and/or other appropriate shaping operations such as sanding, belting drilling, lathing, machining, and/or grinding techniques. These and any other conventional mechanical engagement techniques are referred to herein as mechanical shaping. As it relates to cutting tools, the mechanical operation of milling is often used to form the flutes 18 in the tool body 12. Referring to FIG. 1, this is schematically illustrated where a milling tool 22 is shown mechanically shaping the flutes 12 into the tool body 12. The result of this process forms a metal surface 24 along the flutes 12 of the tool body 12.
As will be readily appreciated by those skilled in the art, it is not possible to provide a perfectly smooth surface as there is always a certain amount of surface roughness after any work operation is performed in commercial applications. This is particularly true as it pertains to complex surfaces, such as, for example, flutes [0021] 18 of the tool body 12, because only rough mechanical shaping operations typically are used to avoid undue labor and expense involved in forming the complex shape of most flutes 18. This is opposed to the treatment of simpler surfaces that are amenable to further refinement, such as the metal surface 27 on other portions of the tool body 12, such as the cylindrical shank portion, which is typically refined and relatively smooth due to finer and more refined mechanical shaping operations such as lathing.
As such, remaining surface roughness on the [0022] metal surface 24 of the flutes 12 after a mechanical shaping operation is a common surface feature of cutting tools. This is schematically indicated in FIG. 2, which is intended to schematically illustrate surface roughness on the metal surface 24 of one of the flutes 18 remaining after a milling operation. Variation in surface roughness often occurs as illustrated by the larger peaks 38 and smaller peaks 38 a, and the defined larger valleys 40 and smaller valleys 40 a between peaks.
Also for purposes of illustration, FIG. 3 is a picture of a microscopic SEM image taken at 300 power magnification of a laboratory mount sample [0023] 100 after a mechanical shaping operation that shows how directional characteristics develop after mechanical shaping. As shown therein, laboratory mount sample 100 has a non-isotropic, directional characteristic due to the direction in which the mechanical shaping operation engages the laboratory mount sample 100. All mechanical shaping operations that engage the surface generally parallel to the surface will leave a directional finish.
Before turning to further description, it should be noted that the designators a-d used for FIGS. 1 and 2 and for [0024] reference character 24 are meant to indicate the sequential steps and progress of the method and surface for a preferred embodiment.
After the tool body is mechanically shaped and the [0025] flutes 18 are milled or otherwise mechanically formed into the tool body 12, the tool body 12 is subjected to a suitable smoothing operation, which preferably removes directional surface characteristics, and more preferably substantially removes the directional surface characteristics, in the complex surfaces of the tool body. In a preferred embodiment, the smoothing operation is provided by a combination chemical treatment and burnishing operation 25 (also referred to herein as chemically smoothing), e.g., as shown in FIG. 2a, to smooth out the peaks 38, 38 a occurring across the relatively rough metal surface 24 in the flutes 18 and to substantially remove any directionality of the metal surface that can result from mechanical shaping operations. For cutting tools, chemically smoothing preferably is conducted without any sharpened cutting edges on the tool body 12, and in the case of the illustrated indexable cutting tool 10, the cutter inserts 14 are removed for this operation to avoid rounding and dulling of the cutting edges of the cutter inserts.
Chemical smoothing can be performed using any suitable process such as, for example, subjecting the cutting tool to a metal reactant and a burnishing substance in an environment of mechanical agitation. For example, as shown FIG. 1[0026] a, the tool body 12 is placed in a vibratory bowl 26 containing burnishing pieces 28 and an aqueous solution of metal reactant 30 can be introduced and/or circulated via an inlet pipe 32. Alternatively, a tumbling basket or other suitable agitating mechanism may be used in alternative embodiments. The vibratory bowl 26 is vibrated by a motor 34 which fluidizes the burnishing pieces 28 and circulates the aqueous solution of metal reactant 30. During this vibratory process, the metal surface 24 a is constantly wetted with the aqueous solution of metal reactant 30. The metal reactant 30 is of the type that reacts with the metal surface 24 a to create a removable thin soft film 36 over the metal surface 24 a. For example, a metal oxidizing agent that reacts with metal to form a soft metal oxide film may be used to create a readily removable layer. Although, the entire metal surface 24 a will quickly become covered with a layer of soft metal film 36, the action and impact of the burnishing pieces 28 imparted by the vibratory action continuously removes this soft metal film 36. Because the burnishing pieces 28 impact or are naturally most prone to impact and scour the higher peaks and elevated portions 38 rather than valleys 40 occurring in the metal surface, the burnishing action tends to impact and remove primarily the soft metal film 36 across the elevated portions or peaks 38, 38 a (which are immediately rewetted with metal reactant to create a new soft removable film across the peaks). This effectively smoothes the metal surface 24 a as is shown and substantially removes the surface directionality that may be imparted by prior mechanical shaping operations. As a result, the surface roughness of the metal surface can be virtually eliminated, except for some of the valleys and the substantially smoothed outline of very large ridges 38 which can often be created during milling operations of tool body 12 to create the flutes 18.
Preferably, the burnishing [0027] pieces 28 are “non-abrasive” in that they are softer than the unreacted metal mass of the tool body 12 but harder than the soft metal film 36 that is formed. Suitable materials for the burnishing pieces 28 can include, for example, porcelain materials and the like. In some applications, it may be desirable to introduce abrasive particles into the burnishing media, particularly where a very large surface roughness characteristic is present. However, the use of conventional abrasive based media (abrasive to the underlying hard metal of the tool body 12) are rarely used due to the invasiveness and changes in tool geometry that can occur when such media are used. Suitable burnishing pieces 28 should preferably include pieces that are small enough to enter the flutes 18 and contact substantially all of the metal surface 24 a to better ensure that the metal surface 24 a of the flutes 18 are smoothed with this chemical smoothing operation 25.
Suitable types of materials, chemicals and processes that may be used for the chemical smoothing operation are disclosed in U.S. Pat. Nos. 5,158,629; 5,158,623; 5,051,141; 4,906,327; 4,818,333; 4,705,594; 4,491,500; and RE 34,272; all of which are owned by REM® Chemicals, Inc. and all of which are hereby incorporated by reference in their entireties. The preferred chemicals and processes used for this step of the invention are commercially available from REM® Chemicals, Inc. located in Southington, Conn. under the brand names FERROMIL® and MAGALLOY®. [0028]
When practicing the invention using the REM® process and products, or other chemical smoothing process and products, it will be appreciated that rate at which the chemical smoothing step proceeds may depend on a number of factors, which include, for example, the nature and concentration of the chemical reactant, the temperature at which the process is performed, the solvents used, the chemical and physical nature of the tool surface, the nature of the surface roughness, and other variables, which are well known to those having ordinary skill in the art. From a vibratory machine operator's standpoint, after the appropriate chemical reactants are selected, the reactant/solvent (e.g., water) ratio and the overall flow rate typically are determined by vibratory machine work zone size. Such variables are addressed, for example, with FERROMIL® chemistry on ferrous metals. The primary variable is the total flow rate of the reactant/solvent (e.g., water) combination. This is recommended to be 0.25 or 32 oz. per cubic foot of bowl size per hour. Thus a 10 cu. Ft. bowl will require 2.5 gal/hr. of total flow per hour. The secondary variable is the chemistry/solvent (e.g., water) ratio. Although suitable concentrations of the reactant can range from about 1 to about 100% percent, common reactants typically are used at concentrations ranging from about 10 to about 50%, and more commonly from about 20-30% for average load densities. The introduction of this mixture is typically accomplished by the use of two precision low-volume pumps. One delivers the proper water volume and the other supplies the chemistry volume. These are simply “piped” to the liquid inlet of the vibratory machine. From a time standpoint, visual and/or microscopic inspection can be done to ascertain how much surface roughness remains to determine length of time needed for this operation. Typically, it will be in the range of about 1-3 hours, but certainly other time periods can be used depending upon the operational parameters and aggressiveness of the operation. [0029]
Preferably, after the chemical smoothing operation [0030] 25 (which is conducted with the aqueous solution of metal reagent 30), it may be desirable to perform a further burnishing operation, e.g., an additional burnishing 42 in a vibratory bowl 45 or other agitator as shown schematically in FIG. 1b, to remove substantially all of the remaining soft metal film 36, leaving substantially only the hard metal mass of the tool body 12, which is resilient and not readily removable. An additional burnishing operation better ensures retention of tungsten disulfide particles. Preferably, the additional burnishing operation 42 includes placing the cutting tool body 12 into a second vibratory bowl 45 or other agitating mechanism containing burnishing pieces 28 and a non-reactive agent such as, for example, water 44 which may be introduced and/or circulated via an inlet pipe 46. As described herein, the burnishing pieces 28 preferably are non-abrasive to the metal of the tool body 12 but are abrasive to the soft metal film 36 that forms across the metal surface 24 b. This burnishing operation 42 preferably removes substantially all of the remaining soft metal film 36 without creating additional soft metal film, such that the outer metal surface 24 b comprises hard steel.
The result of chemical smoothing and additional burnishing applications are schematically shown in FIG. 2, which schematically illustrate the [0031] metal surface 24 b after the chemical shaping operation 25 and after the burnishing operation 42, respectively. In some applications for very rough milled flutes 18, some outlines of large ridges 38 and valleys 40 may remain although the surface over the ridges and valleys is substantially smooth and substantially isotropic (e.g. free of most of the ordinary roughness comprising smaller peaks 38 a and valleys 40 a).
To further illustrate, FIG. 4 is provided which is a picture of a microscopic SEM image taken at 300 power magnification of the surface of the sample laboratory mount sample [0032] 100 after chemical smoothing and burnishing operations. When comparing FIG. 4 (the picture taken after mechanical shaping but prior to chemical smoothing) and FIG. 3 (the picture taken after chemical smoothing and burnishing), it can be seen that the chemical smoothing operation can virtually eliminate most of the ridges and the valleys as well as other surface roughness between formed ridges and valleys. Further, substantially all surface directionality can be removed, making the surface substantially isotropic and substantially smooth.
After the [0033] metal surface 24 b is chemically smoothed and preferably burnished, the surface 24 is then controllably prepared by roughening (pitting) the metal surface 24 c with formed pockets 48. The roughening of the chemically smoothed surface can be accomplished by any suitable method, including, for example, blasting methods which are well known to those having ordinary skill in the art. To illustrate this aspect of the present invention, FIG. 1c schematically depicts a blasting operation 50 where abrasive blast media particles 52 are pneumatically discharged through a blast gun or nozzle 54 and impinged at high velocities against the tool body 12. This roughens the metal surface 24 c and forms the pits or pockets 48 in the metal surface 24 c. This blasting operation 50 prepares the metal surface 24 c for the receipt of tungsten disulfide particles 50. Preferably, the surface 24 c is subjected to the blasting to a degree, which is sufficient to prepare the surface for accepting the tungsten disulfide particles, but is not subjected to excessive blasting that would result in excessive roughening. A preferred method and apparatus for accomplishing this aspect of the present invention is disclosed in further detail in the present patent applicant's prior application, U.S. patent application Ser. No. 10/263,477, filed on Oct. 3, 2003, the entire disclosure of which is hereby incorporated by reference.
According to a preferred preparation method, the parameters of the blasting [0034] operation 50 are controlled to match the size or depth of the pockets 48 to the average size of the tungsten disulfide particles 30 such that the pockets 28 have a depth about equal to or smaller than the average size of the tungsten disulfide particles 56. Commercially laboratory sizes of tungsten disulfide typically have a mean particle size of between about 0.5 micron to about 5 micron. The inventor has found the mean particle size of about 1 micron to provide excellent results.
Once the size of the tungsten disulfide particle to be used in the surface treatment is known, the remainder of the parameters including the size of the blast media used to prepare the [0035] metal surface 24 c and various parameters for the blasting operation 50 can be determined using methods that are well within the skill of the ordinarily skilled artisan. It will be readily appreciated that the hardness and material characteristics of the tool body 12 being treated will affect the operating parameters of the blasting operation.
Because [0036] flutes 18 typically may have a metal surface 24 with relatively large longitudinally extending ridges 38 and valleys 40 as a result of the difficulties in milling the flutes due to their complex configuration, there is presently no commercially practical method for quantifying roughness characteristics of a fluted surface. This is true even after the surface 24 of the flutes 18 is smoothed and rendered substantially isotropic after the chemical treatment and burnishing operation 25. Flutes of different shapes and sizes of cutting tools will also have substantially different roughness characteristics based upon the type of mechanical shaping tools and processes used to form the flutes. These issues make it difficult to provide for a consistent way to quantify and measure the surface roughness using a profolometer as surface readings are likely to have too many discrepancies for meaningful use. Further, organized the larger ridges and valleys that longitudinally with the flutes 18 are not generally problematic since the flutes do not form an actual bearing or hard contact surface but merely convey chips longitudinally and parallel to such ridges and valleys. As a result, the parameters selected for the blast operation can most efficiently be done without any actual measurement readings of the flute surfaces, but may be accomplished using blast parameters that are known to be successful for other metal surfaces formed on a body of the same material or a material of similar hardness.
On the other hand, quantitative measurements, such as profolometer readings, may be taken across the cylindrical shank portion of the tool body [0037] 12 (or a sample laboratory mount, and example of which is herein described) which, in contrast to the flutes, is typically very smooth as a result of lathe turn down and/or more refined mechanical shaping operations, and even smoother after the application of the REM® process described above. Using profolometer readings, the teachings of my prior patent application (application Ser. No. 10/263,477) can be used to optimize parameters, such as media size, for the blast operation 50.
In this regard, four basic parameters that determine the prepared metal surface profile include blast media particle shape, blast media particle size, blast media particle velocity (which is determined primarily by the nozzle characteristic and the operating pressure of the blast machinery, and which can be affected by the feed rate of blast media), and angularity of the particle stream in relation to the [0038] tool body 12. In roughening the tool body 12 for receipt of tungsten disulfide particles 56, preferred materials and ranges include:
a. Blast Media Grit Types: Aluminum Oxide or Silicon Carbide; [0039]
b. Blast Media Grit Sizes: typically greater than 200 grit (preferably greater than 400 grit, and more preferably from about 800 to about 2400 grit); [0040]
c. Gun Pressure: 50-200 psi; and [0041]
d. Blast media carrier gasses, such as, for example, compressed air, pressurized nitrogen, and the like. [0042]
Preferably, the nozzle of the blast gun should be directed generally perpendicular relative to the cutting tool and metal surfaces thereon during blasting operations to avoid imparting directionality on the surface. When the stream of blast media engages a surface perpendicularly, no direction is generated on the surface, which maintains the generally isotropic characteristics that are generated with the REM® process. [0043]
For purposes of illustration, FIG. 2 schematically illustrates the result of the surface preparation and roughening step in which formed [0044] pockets 48 are pitted into the metal surface 24 c. Also, to illustrate what typically happens, FIG. 5 is provided which is a picture of a microscopic SEM image of the laboratory mount sample 100 taken at 300 power magnification after the laboratory mount was subjected to a blasting operation with 1200 grit size blast media at an operational stage subsequent to the REM® FERROMIL® process to roughen the surface of the laboratory mount sample 100.
Once the [0045] metal surface 24 c has been blasted to provide the formed pockets 48, the pockets 48 can be filled with tungsten disulfide particles 56 with a tungsten disulfide coating operation 55 as schematically shown in FIG. 1d. Air blasting may be used to provide for high velocity impingement of tungsten disulfide particles 56 over the metal surface 24 and is the preferred method for providing a tungsten disulfide coated metal surface 24 d. The result is a tungsten disulfide layer 58 across the metal surface 24 d that is about one tungsten disulfide particle thick (e.g. about 1 micron thick if using 1 micron diameter particles). With a substantial number of the pits or pockets 48 preferably being dimensioned smaller in size than the tungsten disulfide particles 56, the tungsten disulfide particles 32 project from the formed pockets 48 to form a sliding surface for external interaction. The tungsten disulfide layer 58 effectively covers and provides a smooth dry lubrication layer on the metal surface 24 d.
It has been surprisingly and unexpectedly found that the [0046] tungsten disulfide layer 58 prepared in accordance with the present invention results in a significant improvement in the ability of chips to slide across the metal surface 24 d of the flutes 18, minimizing the direct contact between the metal surface 24 d and the chips. This effectively prevents surface galling, improves chip evacuation preventing chip packing and prevents wear or erosion behind the cutting edges and the contact surfaces of the tool, significantly increasing the useful life of the tool, without changing critical geometries or dulling the cutting edges, particularly for indexing tools. The method of the present invention, for example, avoids subjecting the cutter inserts 14, which provide the sharp cutting edges and have the most critical geometries are not subjected to the chemical smoothing process (which tends to remove sharp peaks), and also avoids subjecting the cutting inserts to abrasive media blasting operations. Further, the improvement in chip evacuation allows an increase in metal removal rates resulting in increases in machining productivity. The present inventive process can also allow cutting tool manufacturers the ability to eliminate costly heat treatment and nitriding operations, thereby cutting a substantial amount of expense. Of course, if desired, heat treatment of the tool body and/or hardening techniques may still be done in addition to the finishing process of the present invention to further enhance tool life. Considering the economics of cutting tool cost and tool life, however, it is anticipated that such heat treatments will probably be done in some limited applications but will not be done in the vast majority of applications.

Illustrative Example

As discussed above, laboratory mount samples [0047] 100 have been used and are shown at various stages in FIGS. 3-6 to illustrate and provide a greater understanding of the invention, and such laboratory mount samples may be used to develop operating parameters for practicing the invention. For practical reasons described above (e.g. flutes are spiral shaped or otherwise not flat), meaningful profolometer readings cannot be readily obtained on the flutes. By using the laboratory mount sample 100, meaningful profolometer readings can be obtained to give insight upon what is happening and to attempt to optimize operating parameters.
Referring to FIGS. 3-6, there are shown laboratory mount samples [0048] 100 that were ground and polished to an optically flat surface without any visible surface irregularities. Material was a medium-alloy chrome/molybendium alloy commonly referred to 4140 hardened and tempered to 30 HRC. This material is very similar to commercially available 4340, both of which represent the most common material that is used in indexable and brazed-on carbide tooling.
Referring to FIG. 3, the results of a mechanical shaping operation is depicted. To simulate surface roughness similar to milling of the flutes, the laboratory mount sample [0049] 100 was contacted on a 12″ diameter silicon carbide abrasive paper at 200 rpm for a period of 5 seconds. FIG. 3 represents “machined” surface comprised of “peaks and valleys”. When measured with a profolometer, the resultant Ra reading was about 15.
FIG. 4 shows a laboratory mount sample [0050] 100 that was then processed with FERROMIL® chemistry in a 4 cu. Ft. rotary vibratory bowl with non-abrasive media at a concentration of 25% chemistry/water concentration for a period of 90 minutes resulting in a visible isotropic surface a viewed on an illuminated microscope at 40×. The Resultant Ra after this operation was about 2.5.
FIG. 5 shows a laboratory mount sample [0051] 100 that was then processed by the tungsten disulfide roughening process resulting in rougher surface Ra of about 4.5. The process parameters used include a 1200 grit aluminum oxide media, standard vapor blast gun with an air jet size of 0.1875 in. diameter and a nozzle diameter of 0.375 in. with a nozzle pressure of 150 psi, at an engagement distance of 2 in. for a period of 1 sec.
FIG. 6 shows a laboratory mount sample [0052] 100 that was then processed by the tungsten disulfide coating process using high velocity impingement resulting in a surface Ra of 2.5. The process parameters included a tungsten disulphide media mean particle size of 1 micron, standard vapor blast gun with an air jet size of 0.1875 in. diameter and a nozzle diameter of 0.375 in. with a nozzle pressure of 150 psi, at an engagement distance of 2 in. for a period of 1 sec.
All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. [0053]
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. [0054]
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context. [0055]

Claims

What is claimed is:

1. A method of manufacturing and finishing a tool body of a cutting tool, comprising:

mechanically shaping the tool body of the cutting tool to provide a metal surface on the tool body with a first surface characteristic; thereafter

chemically treating the metal surface with a metal reactant to create a relatively soft metal film along the metal surface and removing the soft metal film to smooth the metal surface to a second surface characteristic that is smoother than the first surface characteristic; thereafter

roughening the metal surface; and

coating the roughened metal surface with tungsten disulfide.

2. The method of claim 1, wherein the step of mechanically shaping comprises at least one mechanical operation selected from the group consisting of machining, milling, and lathing, wherein the first surface characteristic of the metal surface has a directional disposition, and wherein the step of chemically treating and removing substantially removes the directional disposition leaving the metal surface with an substantially isotropic finish and thereby providing the second surface characteristic.

3. The method of claim 1, wherein the roughening comprises blasting the metal surface with blast media to form pits in the metal surface.

4. The method of claim 3, wherein said tungsten disulfide comprises tungsten disulfide particles, wherein said coating comprises impinging tungsten disulfide particles on the metal surface to fill the pits with tungsten disulfide particles.

5. The method of claim 5, further comprising selecting a blast media size and operating parameters for the blasting to control the size the pits to be smaller than a size of the tungsten disulfide particles, whereby a substantial number of the tungsten disulfide particles project outside of the pits.

6. The method of claim 3, wherein the blast media has a size of between 200-1800 grit size.

7. The method of claim 1, wherein the cutting tool comprises a metallic tool body and a carbide cutting edge.

8. The method of claim 1, wherein said coating comprises impinging the roughened metal surface with tungsten disulfide particles having a mean particle size of between about 0.5 and about 3 micron.

9. The method of claim 1, wherein the step chemical treating and removing comprises placing the tool body in a vibratory bowl having a plurality of abrasive and/or non-abrasive media particles and the metal oxidizing agent in an aqueous form, and vibrating the bowl to simultaneously form the metal film with the metal oxidizing agent and remove the film with the abrasive and/or non-abrasive media particles.

10. The method of claim 9, further comprising burnishing the tool body in a vibratory bowl containing a plurality of non-abrasive media particles.

11. The method of claim 1, wherein said mechanical shaping comprises milling axially extending flutes into the tool body, the flutes defining the metal surface.

12. The method of claim 1, further comprising nitriding the tool body to harden the tool body.

13. The method of claim 1, further comprising, mounting cutters to the tool body at a time after the chemically treating so as to prevent erosion of sharpened edges on the cutters.

14. A method of finishing a metal surface on a tool body of a cutting tool, the metal surface having a directional characteristic created by a mechanical shaping operation, the method comprising:

smoothing the metal surface and removing the directionality on the metal surface to provide the metal surface with a substantially isotropic surface characteristic; thereafter

pitting the metal surface to forming pits in the isotropic surface; and

filling the pits with tungsten disulfide particles.

15. The method of claim 14, wherein the pitting comprises blasting the metal surface with blast media to form pits in the metal surface.

16. The method of claim 14, wherein said filling comprises impinging tungsten disulfide particles on the metal surface to fill the pits with tungsten disulfide particles.

17. The method of claim 15, further comprising selecting a blast media size and operating parameters for the blasting to control the size the pits to be smaller than a size of the tungsten disulfide particles, whereby a substantial number of the tungsten disulfide particles project outside of the pits.

18. The method of claim 17, wherein the blast media has a size of between 200-1800 grit size.

19. The method of claim 14, wherein the cutting tool comprises a metallic tool body and a carbide cutting edge.

20. The method of claim 14, wherein said filling comprises impinging the roughened metal surface with tungsten disulfide particles having a mean particle size of between about 0.5 and about 3 micron.

21. The method of claim 1, wherein the step smoothing and removing comprises placing the tool body in a vibratory bowl having a plurality of abrasive and/or non-abrasive media particles and the metal oxidizing agent in an aqueous form, and vibrating the bowl to simultaneously form the metal film with the metal oxidizing agent and remove the film with the abrasive and/or non-abrasive media particles.

22. The method of claim 21, further comprising burnishing the tool body in a vibratory bowl containing a plurality of non-abrasive media particles.

23. The method of claim 14, wherein said tool body comprises axially extending flutes formed into the tool body, the flutes defining the metal surface.

24. The method of claim 14, further comprising nitriding the tool body to harden the tool body.

25. The method of claim 14, further comprising, mounting cutters to the tool body at a time after the chemically treating so as to prevent erosion of sharpened edges on the cutters.

26. A method of finishing a metal surface a tool body, comprising:

chemically forming a soft metal film on the metal surface;

removing the soft metal film to smooth the metal surface; thereafter

impinging the metal surface with blast media to form pits in the metal surface; and

impinging the metal surface with tungsten disulfide particles.

27. The method of claim 26, wherein said filling comprises impinging tungsten disulfide particles on the metal surface to fill the pits with tungsten disulfide particles.

28. The method of claim 26, further comprising selecting a blast media size and operating parameters for the impinging to control the size the pits to be smaller than a size of the tungsten disulfide particles, whereby a substantial number of the tungsten disulfide particles project outside of the pits.

29. The method of claim 26, wherein the blast media has a size of between 200-1800 grit size.

30. The method of claim 26, wherein the cutting tool comprises a metallic tool body and a carbide cutting edge.

31. The method of claim 26, wherein the tungsten disulfide particles have a mean particle size of between about 0.5 and about 3 micron.

32. The method of claim 26, wherein the chemically forming and removing comprise placing the tool body in a vibratory bowl having a plurality of abrasive and/or non-abrasive media particles and the metal oxidizing agent in an aqueous form, and vibrating the bowl to simultaneously form the metal film with the metal oxidizing agent and remove the film with the abrasive and/or non-abrasive media particles.

33. The method of claim 32, further comprising burnishing the tool body in a vibratory bowl containing a plurality of non-abrasive media particles.

34. The method of claim 26, wherein said tool body comprises axially extending flutes formed into the tool body, the flutes defining the metal surface.

35. The method of claim 26, further comprising hardening the tool body.

36. The method of claim 26, further comprising mounting cutters to the tool body at a time after the chemically treating so as to prevent erosion of sharpened edges on the cutters.

37. A cutting tool comprising a tool body defining a substantially isotropic surface having pits formed therein, and tungsten disulfide particles filled into the pits.

38. The cutting tool of claim 37, further comprising cutters formed separate from the tool body, the cutters being mounted to the tool body.

39. The cutting tool of claim 38, wherein the cutters comprise carbide material, each cutter providing a cutting edge, and wherein the tool body comprises metallic material, whereby the cutting tool is categorized as a brazed in carbide tool or an indexable tool.

39. The cutting tool of claim 37, further comprising flutes formed into the tool body, the flutes being coated with tungsten disulfide particles.

40. The cutting tool of claim 37, wherein the pits are selectively sized such that a substantial number of tungsten disulfide particles project outside of the pits.

41. The cutting tool of claim 37, wherein the tungsten disulfide particles have a mean size of between .5 and 3 micron.

42. The cutting tool of claim 37, wherein the substantially isotropic surface extends substantially over the entire surface of the tool body.