Abstract: A ceramic material for use as a cutting tool in the high speed machining of high temperature alloys and cast irons is provided with a composition of beta prime sialon (Si.sub.6-z Al.sub.z O.sub.z N.sub.8-2 ; where 1<Z<3) and intergranular phase. The material has high wear resistance and reliability when used in the high speed machining of high temperature alloys at speeds of 300 to 1500 surface feet per minute.

Abstract: A method of manufacturing a shaped ceramic article by hot isostatic pressing comprising the following steps: (a) forming a compact of sinterable ceramic compositions, (b) applying a coating to the compact by vapor deposition of a ceramic composition that does not become vitreous before or during the subsequent isostatic pressing step, and (c) heating and isostatically pressing the coated compacts in an atmosphere that reacts with the coating and/or the compact at pressing temperatures and pressures to cause the compact to approach theoretical density. The method is suitable for forming a fired ceramic compact having a whisker loading in excess of about 12.5 volume percent with substantially isotropic properties due to a substantially random orientation of the whiskers.

Abstract: A method of surface alloying a sialon article containing beta-prime-sialon phase (Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z). The method includes the steps of applying an alumina coating to the surface of the sialon article by chemical vapor deposition and then heat treating the coated article at a temperature between about 1300 and 1800 degrees Centigrade for a time sufficient to diffuse some or all of the aluminum and oxygen from the alumina coating into the sialon composition to produce a layer containing beta-prime-sialon phase having an increased Z value compared to the beta-prime-sialon phase in the remainder of the article.

Abstract: A ceramic composite is provided possessing a combination of high fracture toughness, high hardness and high wear resistance. The composite contains SiC particles dispersed in a ceramic matrix of mainly sialon. The sialon is composed of about 10 to 67 weight percent alpha prime sialon, with the remainder, being beta prime sialon.

Abstract: A method of manufacturing a shaped ceramic article by hot isostatic pressing comprising the following steps: (a) forming a compact of sinterable ceramic compositions, (b) applying a coating to the compact by vapor deposition of a ceramic composition that does not become vitreous before or during the subsequent isostatic pressing step, and (c) heating and isostatically pressing the coated compacts in an atmosphere that reacts with the coating and/or the compact at pressing temperatures and pressures to cause the compact to approach theoretical density. The method is suitable for forming a fired ceramic compact having a whisker loading in excess of about 12.5 volume percent with substantially isotropic properties due to a substantially random orientation of the whiskers.