Surface coated Sialon-base ceramic materials for tools

A surface coated sialon-base ceramic material for wear resistant tools, comprising:

• a sialon-base ceramic matrix which consists essentially of
• (a) 3-30 percent by volume of at least one selected from the group consisting of the carbide of each of the metals exclusive of Cr in the groups 4a, 5a, and 6a of the periodic table of elements, nitride thereof, oxide thereof, and solid solution of at least two of said carbide, said nitride, and said oxide;
• (b) 1-20 percent by volume at least one combined phase-forming component selected from the group consisting of the oxide of Li, Na, Ca, Mg, Y, any rare earth element, Si, and Al, and nitride thereof;
• and
• (c) the balance of .beta.-sialon expressed by the chemical formula Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z, z being larger than 0 but not more than 4.3, and .alpha.-sialon expressed by the chemical formula M.sub.x (Si,Al).sub.12 (O,N).sub.16, x being larger than 0 but not more than 2, M representing at least one selected from the group consisting of Li, Na, Ca, Mg, Y, and any rare earth element, and inevitable impurities, wherein the ratio of the .alpha.-sialon/.beta.-sialon is within a range from 5/95 to 95/5 in volume;
• and
• at least one hard first coating layer formed on a surface of said matrix, said at least one hard coating layer being formed of at least one selected from the group consisting of carbide of Ti, Zr, and Hf, nitride thereof, carbo-nitride thereof, carbo-oxide thereof, and carbo-nitro-oxide thereof.