GB2114041A - Cemented carbide cutting tools and processes for making and using - Google Patents

Abstract

A resharpenable cemented carbide cutting tool, performing one of either cutting or shearing in use, has a cutting edge 9, which is formed by the intersection of two surfaces 5 and 11; only one surface out of the two is treated by ion implantation at a region adjacent to said cutting edge. The surface to be treated by ion implantation is so chosen to be the one i.e. 11 that is subjected to relatively greater wear compared to the other surface; said other surface 5 can be ground to resharpen the tool. A method of making and using these tools is described. The benefits of the initial ion implantation on cemented carbide tool life will remain after sharpening of the tool. <IMAGE>

Description

SPECIFICATION Cemented carbide cutting tools and processes for making and using The present invention relates to the field of cemented carbide cutting tools having a wear resistant layer beneath their surface. This invention is particularly pertinent to those cemented carbide cutting tools which are typically sharpened and reused at least once after some use and consequent dulling of the cutting edge; the tools in question are used to cut material, especially metallic material, by a shearing mode.

It has recently been found that high energy ion implantation can be a useful technique for improving the production lifetime of cemented carbide metal forming tooling. For example.

Dearnaley et al. U.S. Patent No. 4,105,443 indicates that the production lifetime of cemented carbide wire drawing dies can be significantly improved by carbon ion implantation.

It has also been reported that the lifetime of cemented carbide slitter blades cutting synthetic rubber can be significantly improved by nitrogen ion implantation. However, in this later application it is generally believed necessary to ion implant both adjoining faces forming the cutting edge of the slitter blade. One of the problems this causes is that even though the rate of wear of the cutting edge has been reduced, during the blade's lifetime it will still have to be resharpened in order to get full use out of the blades. It has been generally believed that the ground blade surface (the circumferential surface) would then have to be reimplanted to retain improved wear resistance.

This is both inconvenient and costly to the tool user.

The present invention in its broad form resides in a cemented carbide tool having an edge which performs one of cutting or shearing operations in use, comprising: a first surface containing said edge; a second surface joining said first surface at said edge; a cemented carbide cutting edge formed at a junction of said first and said second surfaces; an ion implanted wear-resistant layer located adjacent said cutting edge and beneath and parallel to one of said first and second surfaces, said layer intersecting the other of said first and second surfaces; said other surface being devoid of any ion-implanted wear-resistant layer.

Applicants have found that the wear-resistant layer should be preferably made by the process of implantation of high energy ion species. Ion implantation in accordance with the invention forms wear-resistant layers comprising irradiation defects and micro-structural modifications and, a high concentration of the implanted species which may extend inwardly as far as 1000 angstroms, and more typically below 400 angstroms.

Preferably the cutting tools formed in accordance with the method of the present invention are cemented carbide punches and dies for use in perforating material. In these embodiments of the present invention, preferably only the peripheral faces of the punch adjacent to the shearing edge and the wall faces of the die adjacent to the shearing edge are ion implanted.

Also using the present invention applicants have found an improved process for using ion implanted cemented carbide cutting tools. The dulled ion-implanted tool is resharpened and then used again without reimplantation in spite of the ground surfaces. This process of use and resharpening may be repeated many times while still retaining a significant tool life without subsequent reimplantation. This is made possible because of the fact that ion implantation is done on only one surface out of the two surfaces, and the surface which is devoid of ion implantation is preferably the one which is ground for resharpening.

These and other aspects of the present invention will become more apparent upon review of the drawings in conjunction with the following detailed description of a preferred embodiment, which is given only by way of example.

Brief Description of the Drawings Figure 1 shows a pictorial view of a cemented carbide punch using the principles of the present invention.

Figure 2 shows a pictorial view of a cemented carbide die to cooperate with the punch of Figure 1, constructed using the present invention.

Figure 3 shows a cross section through a punch and die using the present invention just prior to perforating a workpiece.

Figure 4 shows another cemented carbide rotary or slitting blade cutting using the present invention.

Figure 5 shows a cross section of the Figure 4 embodiment taken along arrows lV-IV.

As shown, Figures 1 and 2 illustrate punching or shearing tools which have been ion implanted.

In Figure 1 a punch 1 having a first or leading face 5 and a second, flank, peripheral surface or side wall 7 joined to it at a shearing edge 9 is illustrated. The side wall 7 has been ion implanted in the region 11. Ion implantation produces a wear-resistant layer beneath the surface that has been ion implanted. In cemented carbides this layer may extend inwardly from the surface as deep as 1000 angstroms in depth, but is typically below 400 angstroms in depth. The concentration of the species of ion which has been implanted is typically in a gaussian like distribution beneath the implanted surface, however, extending from the implanted surface down to the deepest penetration of the ions are radiation-produced defects and modifications in the micro-structure which have been caused by the high energy ion passing through the material.As can be seen in this Figure, only the peripheral face 7 of the tool has been ion implanted such that a wear-resistant layer 11 is produced beneath and parallel to the flank surface 7 while intersecting the leading face 5 of the punch 1 near the shearing edge 9.

Figure 2 shows a segmented die 3 which has been implanted along its side walls 17 or peripheral surface much in the same manner as the aforementioned punch 1. The segmented die has a leading face 1 5 which is joined to the peripheral surface 17 at a cutting edge 19. The wear-resistant layer 23 lies beneath and parallel to the peripheral surface 17 at 21 and intersects the leading face 1 5 near the cutting edge 19. A segmented die is preferred over a single piece die to facilitate ion implantation of the internal side walls 1 7 of the die since ion implantation is a lineof-sight process and is most efficiently done when the beam is substantially perpendicular to the surface being implanted.

Figure 3 is a cross section through the punch 1 and die 3 of Figures 1 and 2 which are shown here aligned with a sheetlike material 51 between them which is to be perforated. In a perforation operation such as that shown here, the punch 1 interacts with the die walls 17 and cutting edge 1 9 of the punch 3 to punch out a perforation having a shape substantially in accordance with the shape of the leading face of the punch and the cavity in the die 3. The ion-implanted layer 11 in the side wall 7 of the punch and the ion-implanted layer 21 in the side wall of the die 3 while greatly extending the number of perforations that can be made with this tool will not cause the cutting edges 9 or 1 9 to last forever and at some point these cutting edges will have to be resharpened.

Applicants have found that when this occurs the leading faces of the punch 1 and die 3 may be ground back to produce a sharpened edge without additional implantation of the leading faces 5 and 15. The following example illustrates the method and cutting tools according to the present invention.

EXAMPLE A cemented carbide punch and a cemented carbide segmented die were ion implanted to Droduce a wear-resistant layer beneath and parallel to the implanted surfaces and estimated to extend inwardly from these surfaces approximately less than 1000 angstroms. The punch and die having a shape substantially as shown in Figures 1 and 2 were composed of approximately 0.8 to 1.0 micron size tungsten carbide particles bonded together by approximately 14 weight percent cobalt. Both leading faces and the peripheral faces of the punch and die segments were implanted with nitrogen ions having an energy of 90 KeV until a dose of approximately 2 x 10+17 ions/cm2 was achieved in the treated surface areas. The punch and die were then mounted as a set in an index press operating at 900 strokes per minute.

Perforations were made in .022 inch nominal thickness, low carbon steel sheet and also in 0.018 inch nominal thickness, silicon steel sheet in a single stroke, without lubrication, in which the punch traveled through the full thickness of the material. The runs on silicon and carbon steel sheet were intermixed with each other. In this manner a total of 2,100,000 and 1,830,000 perforations in low carbon and silicon steel, respectively, were made before the punch and die required resharpening. A diamond wheel was used to dry-surface grind the lead surfaces of the punch and die until sharp cutting edges were produced.

This grinding step required removal of material to a depth greatly in excess of the original implanted wear-resistant layer. The punch and die were then used without honing of the cutting edges or additional ion implantation to the ground faces, An additional 3,000,000 perforations were then made in carbon steel sheet before a press malfunction aborted the study. Visual examination of the punch and die at this time revealed that the cutting edges were still in an acceptable condition.

The 3,000,000 perforations, however, do represent a significant improvement over the life of unimplanted cemented tungsten carbide punches and dies, which typically produce 1,000,000 perforations in low carbon steel or approximately 500,000 perforations in silicon steel per sharpening.

It can therefore clearly be seen that significant improvement in punch and die life can be obtained due to ion implantation even after the wearresistant layer in one of the faces adjoining the cutting edge of the tool has been removed.

Therefore, it is also believed that significant improvements in punch and die life can be obtained where, during the original implantation step, only the peripheral surfaces or side walls of the tools are implanted such that the wearresistant layer produced intersects the leading face of the tool as shown in the Figures.

While the present invention has been illustrated by its application to cemented carbide punch and dies, it is not limited to the embodiments. Also, as shown in Figures 4 and 5, it is found that cemented carbide slitter blades 40 which have an ion-implanted wear-resistant layer only in their side walls 44 can achieve significant increased lifetime over unimplanted blades. This means that the originally implanted blade 40, whether it was implanted solely on its side walls 44 or on its side walls 44 and circumferential surface 42 can be resharpened by grinding of the circumferential surface 42 leaving only the thin wear-resistant layer 48 beneath and parallel to the side walls 44 and intersecting the circumferential wall 42 near the cutting edge 46. In this manner the benefits of ion implantation can be extended throughout the lifetime of the blade without reimplantation of ground surfaces after each sharpening.

The above embodiments of this invention are exemplarily illustrative and do not limit the scope of invention, which is covered by the following

Claims (8)

claims. CLAIMS

1. A cemented carbide tool having an edge which performs one of cutting or shearing operations in use, comprising: a first surface containing said edge; a second surface joining said first surface at said edge; a cemented carbide cutting edge formed at a junction of said first and said second surfaces; an ion implanted wearresistant layer located adjacent said cutting edge and beneath and parallel to one of said first and second surfaces, said layer intersecting the other -of said first and second surfaces; said other surface being deviod of an ion-implanted wearresistant layer.

2. The cemented carbide cutting tool according to claim 1 wherein said wear-resistant layer includes irradiation-damaged metal carbide particles and irradiation-damaged modified metallic binder.

3. The cemented carbide cutting tool according to claim 2 wherein said wear-resistant layer includes a foreign species implanted by ion implantation.

4. The cemented carbide cutting tool according to claim 1 wherein said intersection of said wearresistant layer with said other surface provides a wear-resistant zone up to approximately 3000 angstroms wide on said other surface.

5. The cemented carbide cutting tool according to claim 1 wherein said wear-resistant layers extends inwardly to a depth of 400 angstroms maximum.

6. The cemented carbide cutting tool according to claim 3 wherein said foreign species is nitrogen

7. A process of fabricating a cemented carbide tool to increase tool life by ion implantation, said process comprising the steps of: forming a cutting edge at a junction of two cemented carbide surfaces meeting at ån angular edge on said tool; and implanting ions into one of said cemented carbide surfaces at said cutting edge, the other surface being generally devoid of ion implantation.

8. The process according to claim 7 wherein said step of ion-implanting is performed on only one of said cemented carbide surfaces, by high energy ion species