Method for making high performance self-reinforced silicon carbide using

Abstract

A sintered silicon carbide (SiC) body prepared by a process which contains the steps of: (a) preparing a raw batch containing: (i) a raw silicon carbide mixture containing about 10 to about 90 weight percent of an .alpha.-phase SiC powder and about 90 to about 10 weight percent of a .beta.-phase SiC powder; (ii) aluminum oxide (Al.sub.2 O.sub.3) powder, about 3 to 15 weight percent of the raw silicon carbide mixture; (iii) yttrium oxide (Y.sub.2 O.sub.3) powder, about 2 to 10 weight percent of the raw silicon carbide mixture; (iv) an organic binding agent and a dispersing agent; and (v) deionized water; (b) drying the raw batch to form a green body; (c) heating the green body at temperatures between about 400.degree. and 800.degree. C. to remove the organic binding agent and the dispersing agent; and (d) subjecting the green body to a two-stage pressureless sintering process, first at a first sintering temperature between about 1,800.degree. and about 1,950.degree. C. for 0.5 to 8.0 hours, then at a second sintering temperature between about 1,900.degree. and about 2,200.degree. C. for 0.1 to 4 hours, wherein the second sintering temperature is selected such that it is higher than the first sintering temperature. The sintered silicon carbide bodies were measured to have a flexural strength of at least 500 MPa, measured using a four-point method; and a fracture toughness of at least 5.0 MPa-m.sup.0.5, measured based on a precrack thickness of 0.15 mm.