FIELD

The present invention relates to methods of making metal matrix composite and alloy articles and, in particular, to freestanding metal matrix composite and alloy articles having complex geometry, thin wall structure and/or thin cross-section.

BACKGROUND

Fabrication of hard alloy or metal matrix composite articles is always challenging since brittleness typically increases with increasing hardness. Fabrication of hard alloy or metal matrix composite articles having complex geometry, thin wall thickness or thin cross-section is particularly challenging. Fabrication techniques such as pre-forming by powder pressing, extrusion or injection molding followed by sintering are often employed for making such articles. However, given the limitations of tooling and dies, articles produced according to these methods are usually not near-net shape, necessitating additional significant green shaping, machining and processing.

Moreover, casting can be used for making articles of complex geometry and thick wall structure. Nevertheless, casting is mainly limited to a subset of metal and alloy systems suitable for such operations. For hard alloys and metal matrix composites, casting can be difficult. Further, mechanical working, such as hot rolling, is sometimes employed for making thin metal or alloy sheets. Hard alloys and metal matrix composites are generally unsuitable for hot rolling due to the high hardness exhibited by these materials rendering them brittle and prone to crack formation during the working process. In view of these deficiencies, new methods of producing hard alloy and metal matrix composite articles, including articles of complex geometry, thin wall structure or thin cross-section, are required.

SUMMARY

In one aspect, methods of making freestanding metal matrix composite articles are described herein which, in some embodiments, can offer advantages over prior methods. Advantages of methods described herein can be fully exploited when fabricating metal matrix composite articles and alloy articles of complex geometry, thin wall thickness and/or thin cross-section. A method of making a freestanding composite article described herein comprises providing a temporary substrate and disposing over a surface of the temporary substrate a layered assembly comprising a layer of infiltration metal or alloy and a hard particle layer formed of a sheet comprising organic binder and the hard particles. The layered assembly is heated to infiltrate the hard particle layer with the metal or alloy providing a metal matrix composite, and the metal matrix composite is separated from the temporary substrate. Infiltration alloy, in some embodiments, comprises nickel-based alloy, cobalt-based alloy, copper-based alloy, iron-based alloy, aluminum-based alloy or titanium-based alloy. Further, in some embodiments, infiltration metal or alloy is added to the sheet comprising organic binder and the hard particles and, therefore, is not provided as a separate layer in the assembly.

In another aspect, methods of making freestanding metallic articles are described herein. The freestanding metallic articles can be of complex geometry, thin wall structure and/or thin cross-section. A method of making a freestanding metallic article comprises providing a temporary substrate and disposing over a surface of the temporary substrate a sheet comprising organic binder and powder metal or powder alloy. The sheet of organic binder and powder metal or powder alloy is heated to provide a sintered metal or sintered alloy article, and the sintered metal or sintered alloy article is separated from the temporary substrate.

These and other embodiments are described in greater detail in the detailed description which follows.

