US3525999A - Carbide alloys - Google Patents

Description

United States Patent Oifice 3,525,999 CARBIDE ALLOYS Friedrich Benesovsky, Tirol, and Richard Kielfer, Vienna, Austria, assignors to Ugine-Carbone, Paris, France, a corporation of France No Drawing. Filed Dec. 24, 1968, Ser. No. 786,745 Int. Cl. C22c 29/00 U.S. Cl. 29--182.7 6 Claims ABSTRACT OF THE DISCLOSURE A carbide alloy consisting essentially of WC, TiC, TaC, HfC and Co. Up to 25 by weight of TaC may be associated NbC. The TaC, associated NbC, and HfC total between 3 and 25 by weight of the alloy. The weight ratio of the TaC and associated NbC to the HfC must be between 2:1 and 1:4.

Originally, cemented or sintered carbide products were composed of WC and Co. Carbide products are well known as cutting tools. Carbide alloys comprising WC- TiC-Co and WC-TaC-Co were developed for tooling long chipping work materials. In the past ten years, combined carbide alloys comprising WC-TiC-TaC-Co have been developed. Depending on the particular use to which these new alloys were put, they contained 5 to 40% TiC, 3 to 20% TaC, 6 to 18% Co and the remainder WC. Preferably, they comprise to 20% TiC, 5 to 12% TaC, 7 to 11% Co and the remainder WC.

In the past, substitution of other carbides for the TiC and TaC were made but did not produce any particular beneficial result. Thus, for example, in place of the TiC the carbide ZrC and HfC were used, and in place of TaC the carbides VC and NbC and also HfC were used.

It has now been found that a partial replacement of the TaC by HfC in the WC-TiC-TaC-Co alloys results in a carbide alloy that had a surprising degree of toughness andbending resistance. Such a carbide alloy consists essentially of WC, TiC, TaC, HfC and Co. Up to 25% by weight of the TaC may'be associated NbC. The TaC, associated NbC, and HfC generally total between 3 and 20% and may total as high as 25% by weight of the alloy. The weight ratio of the TaC plus associated NbC to HfC must be between 2:1 and 1:4. Preferably, the carbide alloys according to this invention consist essentially of 3 to 40% by weight of TiC, 3 to 25% Co, 5 to 20% total TaC plus associated NbC plus HfC and the remainder WC. An optimal carbide alloy according to this invention consists essentially of 10 to 20% by weight TiC, 7 to 11% Co and 5 to 15% TaC plus associated NbC plus HfC and the remainder WC. The best mode now known for practicing this invention which mode provides the maximum fiexural resistance has been found in an alloy consisting essentially of 15% TiC, 8% Co, 2.5% pure TaC, 2.5% HfC and the remainder WC. Such an alloy exhibits bending resistance values of about 170 to 190 kg./mm. while alloys containing no HfC but having 15% TiC, 5% TaC, 8% Co and the rest WC as well as alloys containing no TaC but having 15% TiC, 15% HfC, 8% Co and the rest WC show values of only 135 to 155 kg./mm.

It has been found preferable that with larger proportions of total TaC plus HfC by weight of the alloy, the ratio of TaC to HfC should be decreased. Thus, it is preferable when the total TaC plus associated NbC and HfC is greater than 5% but less than and equal to 10% of the alloy, the weight ratio TaC plus NbC to HfC is between 2:1 and 1:2 and when the total TaC plus as- Patented Aug. 25, 1970 sociated NbC plus HfC is greater than 10% and less than 15% of the alloy, the weight ratio of TaC plus NbC to HfC is between 1:2 and 1:4. Sintered carbide alloys may be prepared according to this invention by using the pure vacuum annealed form of TaC and HfC. However, it has proven favorable to use binary solid solutions of TaC and HfC or ternary solid solutions, for example, TaC-HfC-TiC or TaC-HfC-WC or even quaternary solid solutions, for example, TaC-HfC-TiC-WC. In other words, in preparing carbide alloys in accordance with this invention, it is preferable that as much WC and TiC be added at the time of the preparation of the solid solutions as can be maintained in solutions at a subsequent sintering temperature of about 1500 C.

While the scientific basis for the present invention is not entirely understood, it is thought that the surprising mechanical resistance of carbides according to this invention results in a gap in the range of miscibility in the TiC-HfC system. It has been observed by metallographic and X-ray studies that alloys according to this invention are comprised of three phases, a HfC poor WC-TiC-TaC- HfC solid solution, a HfC rich W C-TiC-TaC-HfC solid solution, and WC-Co matrix phase. Carbide alloys containing separate solid solutions have not been observed or utilized in the technology of carbides up until the present invention.

It should be understood that it is within the scope of this invention to add small additions of up to about 3% of other carbides such as VC, Cr C ZrC and Mo C that enhance the hardness thus helping to maintain the cutting edge of tools made from these alloys. The TaC that is used may contain, for example, 5 to 25 NbC found in the usual minerals.

Having thus described the invention in detail and with the particularity required by patent law, what is desired to have protected by Letters Patent is as follows.

We claim:

1. A carbide alloy consisting essentially of WC, TiC, TaC, HfC and Co, up to 25% by weight of TaC being associated NbC, the TaC, associated NbC and HfC totaling between 3 and 25 by weight of the alloy and the weight ratio of TaC plus associated NbC to HfC being between 2:1 and 1:4.

2. A carbide alloy consisting essentially of WC, TiC, TaC, HfC and C0, up to 25 by weight of TaC being associated NbC, the TaC, associated NbC and HfC totaling between 3 and 25% by weight of the alloy and the weight ratio of TaC plus associated NbC to HfC being between 2:1 and 1:4, and including up to 3% of carbide selected from the group VC, Cr C ZrC, M0 0 and mixtures thereof.

3. A carbide alloy according to claim 2 wherein the alloy consists essentially of 3 to 40% by weight TiC, 3 to 25% Co and 5 to 20% TaC plus associated NbC plus Hf 4. A carbide alloy according to claim 3 wherein the alloy consists essentially of 10 to 20% by weight TiC, 7 to 11% Co and 5 to 15% TaC plus associated NbC plus HfC.

5. A carbide alloy according to claim 4 wherein when the total TaC plus associated NbC plus HfC is less than and equal to 10% by weight of the alloy, the weight ratio 4 HfC poor wOTiC-TaC-Hfc solid solution, and a HfC 2,899,739 8/ l959 Ohlsson 75203 XR rich WC-TiC-TaC-HfC solid solution in a WC-Co matrix. 2,188,983 2/1940 Padowicz 29-182.7

References Cited CARL D. QUARFORTH, Primary Examiner UNITED STATES PATENTS 3,463,621 8 /1969 Kieffer 29 1s2.7 3,245,763 4/1966 OlllSSOl'l 29-182.8 XR 2,924,875 2/1960 Gisner 75203 XR 75203 5 A. I. STEINER, Assistant Examiner