Boron-treated hard metal

• US 5,116,416 A
• Filed: 10/09/1990
• Issued: 05/26/1992
• Est. Priority Date: 03/11/1988
• Status: Expired due to Term

• Current Assignee: Credo Technology Corporation
• Original Assignee: Vermont American Corporation (Robert Bosch GmbH)
• Inventors: Knox, Jack D., Pennington, Donald C. Jr.
• Primary Examiner(s): Hunt, Brooks
• Assistant Examiner(s): Jenkins, Daniel J.
• Application Number:
  US07/593,999
• Time in Patent Office: 595 Days
• Field of Search: 75/238, 75/243, 75/244, 75/246
• US Class Current: 75/238
• CPC Class Codes: B22F 2207/01 Composition gradients
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• CPC Class Codes: B22F 9/026 Spray drying of solutions or suspensions
• CPC Class Codes: C22C 1/051 Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor
• CPC Class Codes: C22C 29/08 based on tungsten carbide

Abstract

A hard, relatively non-brittle, cemented carbide body is made by sintering pressed grade carbide powders in the presence of a boron-containing material such as boron nitride. During sintering, appreciable quantities of boron migrate or diffuse into the body to become incorporated throughout the microstructure of the carbide resulting in the formation of a third quarternary phase comprised of tungsten, nickel, boron and carbon.

Claims

1. A cemented carbide body, comprising:

a tungsten carbide phase;

a nickel binder phase; and

a third phase comprising nickel, tungsten, boron, and carbon.

2. A cemented carbide body as recited in claim 1, wherein the ratio by weight of tungsten to nickel in the third phase is greater than 1.0.

3. A cemented carbide body as recited in claim 2, wherein the ratio by weight of boron to carbon in the third phase is greater than 1.0.

4. A cemented carbide body as recited in claim 3, wherein the ratio by weight of boron to carbon in the third phase is between 1.0 and 12.0.

5. A cemented carbide body as recited in claim 1, wherein the tungsten carbide particles are generally angular and blocky in shape but, in the region of the third phase, the tungsten carbide particles are rounded and smaller.

6. A cemented carbide body as recited in claim 1, wherein the average dimensions of the third phase are larger than the average dimensions of the nickel binder phase.

7. A cemented carbide body as recited in claim 6, wherein the amount of boron in the body is between 25 and 3000 parts per million.

9. A cemented carbide body as recited in claim 7 or 8, wherein the distribution of the amount of boron in the body is a controlled gradient, with greater concentrations of boron and the etch phase at the surface and lesser concentrations towards the center of said body.

10. A cemented carbide body as recited in claim 7, wherein said etch phase also includes a greater percent by weight of the carbide former than is found in the binder phase.

11. A cemented carbide body as recited in claim 10, wherein said etch phase, before being etched, includes some of the carbide former, some of the binder element, some carbon, and some boron, and wherein the ratio by weight of carbide former to binder element in the etch phase is greater than 1.0.

8. A cemented carbide body, comprising:

a) a carbide phase, including a carbide former and carbon;

b) a binder phase made mostly of a binder element; and

c) a dispersion of boron-containing material throughout the body, wherein the microstructure of said carbide body, when subjected to track etch analysis and etched with a caustic solution, exhibits an etch phase throughout the body.