Patent ID: 12186807

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings wherein like reference numerals designate identical or corresponding parts throughout the several views, there is illustrated generally atFIG.1a ceramic-metallic composite which has been spherodized. As can be appreciated, the ceramic-metallic composite can have many other shapes. The ceramic-metallic composite inFIGS.1-2is a ceramic rich material that includes a ceramic rich cermet region10that is coated by a metal coating14. The thickness of the coating is sufficient to provide the desired amount of spacing between ceramic rich cermet regions in a heterogeneous body formed from the ceramic-metallic composite10. Typically, the thickness of the coating is about 1 to 40 percent of the diameter of the ceramic rich cermet region, and more typically about 1 to 10 percent of the diameter of the ceramic rich composite ceramic-metallic particle.FIG.2illustrates a more detailed view of the ceramic rich cermet region which is formed of a plurality of ceramic particles16bonded together by a metallic binder12.

There is indicated generally atFIG.3a consolidated composite of particles where coating14forms the ductile metal matrix18when the ceramic-metallic composite are consolidated together. The ceramic rich cermet regions10are illustrated as being spaced apart from one another by the ductile metal matrix18and the ceramic rich cermet region10have generally maintained their shape. This type of consolidated material is typically formed by spark plasma sintering, but can also be formed by another high temperature rapid compaction technique. The mean free path between the ceramic rich cermet regions10is approximately equal to the thickness of the coating14; however, this is not required.

A micrograph of a cross section of consolidated material inFIG.4shows verification of the target structure ofFIG.1in practice. Furthermore, the structure allows for high microfracture toughness as seen in the scanning electron microscope image of the material inFIG.5. The crack propagation at the tips of the nano-indentation is unobservable, indicating high resistance to micro-fracture as the ductile binder blunts crack propagation and the sub-micron hard ceramic particles30limit maximum crack length across a particle. This nano-indent produced no observable cracks within the sample indicating high fracture toughness.

Example 1

A ceramic-metallic composite was produced with a composition of about 45-50 wt % TiN, about 40-45 wt % Co—Mo—Cr, and about 10 weight percent niobium binder. The ceramic-metallic composite was consolidated using spark plasma sintering above about 1000° C. The consolidated material exhibited a hardness of 1278 HV (300) and coefficients of friction of less than about 0.10 in diesel fuel, and about 0.40 in dry contact with steel. No material wear was observed after friction testing with pin on disk tribometer.

Example 2

The material formed in Example 1 was machined using electrical discharge machining into an about 2 in. wide, ¼ in. thick flat thrust bearing with an internal diameter of about 1 in.

Example 3

The material formed in Example 1 was precision-machined using electrical discharge machining into about a 1 in. tall hollow cylinder with about ⅛ in. wall thickness. This cylindrical piece was interference fitted into a steel bushing to form a cermet lined bushing.

Example 4

A ceramic-metallic composite was produced with a composition of about 92-97 weight percent tungsten carbide and about 3-8 wt. % cobalt as the binder and a coating of about 10 weight percent cobalt. The ceramic-metallic composite was consolidated using spark plasma sintering to form about a 2 in. wide by 1.5 in. tall billet. The formed material exhibited a hardness of about 22.95 GPa (2340 HV), a modulus of about 486 GPa, and a fracture toughness greater than about 20 MPa-m1/2. The material was machined to a surface roughness between about 3-5 micro-inch and tested for rolling contact fatigue. The formed material survived in excess of about 60 million stress cycles at about 2.5 GPa without showing any sign of wear or spallation. The formed material also exhibited coefficient of friction as low as about 0.35 in dry conditions, and less than about 0.10 in lubrication or liquid including saltwater.

Example 5

A ceramic-metallic composite similar to that produced in Example 4, but the 10 wt. % cobalt coating was substituted for about 10 wt. % nickel coating. The ceramic-metallic composite was consolidated using spark plasma sintering to form about a 2 in. wide by 1.5 in. tall billet. The formed material exhibited a hardness of about 20.07 GPa (2045 HV), a modulus of about 435 GPa, and a fracture toughness greater than about 20 MPa-m1/2. When machined to a surface roughness between about 3-5 micro-inch and tested for rolling contact fatigue, the formed material survived in excess of about 60 million stress cycles at about 2.5 GPa without showing any sign of wear or spallation. The formed material also exhibited coefficient of friction as low as about 0.35 in dry conditions, and less than about 0.10 in lubrication or liquid including saltwater.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made in the constructions set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. The invention has been described with reference to preferred and alternate embodiments. Modifications and alterations will become apparent to those skilled in the art upon reading and understanding the detailed discussion of the invention provided herein. This invention is intended to include all such modifications and alterations insofar as they come within the scope of the present invention. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention, which, as a matter of language, might be said to fall there between. The invention has been described with reference to the preferred embodiments. These and other modifications of the preferred embodiments as well as other embodiments of the invention will be obvious from the disclosure herein, whereby the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims.