Wear and thermal shock resistant SiAlON cutting tool material

DETAILED DESCRIPTION It is an object of this invention to avoid or alleviate the problems of the prior art.
It is further the object of this invention to provide SiAlON material compositions particularly useful for machining of heat resistant alloys.
In one aspect of the invention there is provided a sintered ceramic material for high speed machining of heat resistant alloys, said ceramic comprising SiAlON and 0.
2-20 v/o intergranular phase whereby at least 80 v/o of said SiAlON phase is beta SiAlON (Si.
sub.
6 --.
sub.
z Al.
sub.
z O.
sub.
z N.
sub.
8-z) having a z-value greater than 1.
0, but less than 1.
5, said sintered ceramic material having a Vickers Hardness HV1 of more than 1530.
In another aspect of the invention there is provided a method of manufacturing the material described above comprising mixing powders, pressing same to form blanks and sintering the blanks using gas pressure sintering whereby the final part of the sintering takes place at 1700.
degree.
C.
-1800.
degree.
C.
and 10-15 bar nitrogen for 1-3 hours.
In yet another aspect of the invention there is provided a method of high speed machining of heat resistant alloys comprising bringing a cutting tool of the material described above into contact with a workpiece of a heat resistant alloy and moving at least one of the cutting tool and the workpiece to remove material from the workpiece.