Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Metal and nonmetal in final product
Reexamination Certificate
1995-08-11
2001-02-06
Jenkins, Daniel J. (Department: 1742)
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Metal and nonmetal in final product
C419S027000, C419S029000
Reexamination Certificate
active
06183687
ABSTRACT:
BACKGROUND
The invention pertains to a hard composite that is made via sintering techniques. More specifically, the invention pertains to a hard composite that is made via sintering techniques that are able to control the extent and depth of cobalt enrichment in the region of the surface of the hard composite.
In hard composites like cemented tungsten carbides, the binder (e.g., cobalt) content has an influence on the properties of the composite. For example, an increase in cobalt content typically leads to an increase in toughness of the composite. Heretofore, there has been a desire to be able to have a binder-enriched region near the surface of a hard composite. For example, United States Reissue Pat. No. 34,180, to Nemeth et al., assigned to the assignee of the present patent application, discloses a method that produces a hard composite with binder enrichment in the surface region, as well as discloses such a product.
Typical applications that would find hard composites that have surface binder enrichment to be desirable would be wear applications, mining applications, construction applications, and metalcutting applications. Wear parts like wire drawing dies would find a hard component with such a microstructure to be advantageous. In the mining applications, mining tools like roof bits, open face style tools, and conical style tools would find a use for a hard insert with a microstructure presenting binder enrichment in the surface region. In the construction applications, rotatable construction tools would find a hard insert with a microstructure presenting binder enrichment in the surface region to be advantageous. In metalcutting applications, a cutting tool that has a microstructure with binder-enrichment in the surface region would be advantageous.
SUMMARY
It is an object of the invention to provide an improved method of making a hard composite with binder-enrichment in the surface region, as well as the hard composite that has binder-enrichment in the surface region.
In one form thereof, the invention is a method of heat treating a sintered body having an exposed surface. The method comprises the steps of: providing a sintered body comprised of a hard carbide and a binder, the binder being present in the sintered body at a first binder level and the hard carbide in the sintered body being of a first grain size; placing granules of a sacrificial sintered material in contact with at least one portion of the exposed surface of the sintered body, the sacrificial sintered material comprised of the hard carbide and the binder, the binder being present in the sacrificial sintered material at a second binder level and the hard carbide in the sacrificial sintered material being of a second grain size; and heat treating the sintered body and sacrificial sintered material so as to change the binder content in a surface region of the sintered body.
In another form thereof, the invention is a hard insert produced by a process comprising the following steps: providing a sintered body comprised of a hard carbide and a binder, the binder being present in the sintered body at a first binder level and the hard carbide in the sintered body being of a first grain size; placing granules of a sacrificial sintered material on at least one portion of the exposed surface of the sintered body, the sacrificial sintered material comprised of the hard carbide and the binder, the binder being present in the sacrificial sintered material at a second binder level and the hard carbide in the sacrificial sintered material being of a second grain size; and heat treating the sintered body and sacrificial sintered material so as to change the binder content in a surface region of the sintered body.
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Santhanam, A. T., et al., “An Advanced Cobalt-Enriched Grade Designed to Enhance Machine Productivity,” Paper 8503-003, at ASM Conference on Machining, May 7-9, 1995, Metals Park, OH.
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Jenkins Daniel J.
Kennametal Inc.
Prizzi John J.
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