Patent ID: 6824727
Filing Date: 2004-11-30
Classification: C04B

Abstract:
A method of preparing SiAlON ceramic material comprising:a) providing a powder mixture of: i. silicon nitride as the major ingredient; ii. 0.1 to 20 parts by weight of an oxide or nitride of Sc, Y, La or a RE; iii. 3 to 20 parts by weight of aluminum nitride; iv. 0.1 to 6.5 parts by weight of an oxide or nitride of Mg and optionally one or of more of Ca, Sr, and Ba; and v. less than 1.5 weight percent aluminum oxide or compounds containing aluminum oxide; b) forming a green compact from the powder mixture; and c) heating the green compact to form a ceramic material with closed porosity, said heating step comprising: c1) an optional first heating step at between 300 and 900Â° C. in a static or flowing non-reactive atmosphere; c2) a second heating step at between 1650 and 1800Â° C. in a static or flowing non-reactive atmosphere; and c3) an optional third heating step in a hot isostatic press at between 1400 and 2000Â° C. under a pressure of a non-reactive gas at a pressure of between 690 KPa and 413 MPa; and d) forming a SiAlON ceramic material into a metal cutting tool insert or a ceramic tool for high speed chip forming of metallic materials.