Patent ID: 6066582
Filing Date: 2000-05-23
Classification: C04B,Y10T

Abstract:
A method of making a silicon nitride cutting tool insert by powder metallurgical methods comprising the steps of:a) preparing a silicon nitride slurry by wet dispersion in water or an organic solvent of silicon nitride powder with powders of yttrium oxide 0.1-5 weight %, aluminum oxide 0.1-5 weight % and one or more transition metal chosen from the group consisting of: niobium oxide, tantalum oxide and mixtures thereof in an amount of 0. 1-5 weight %, whereby the total sum of added oxides is less than 6 weight %, and dispersing agents;b) drying the slurry;c) granulating the dried slurry to form a powder;d) shaping the powder to form a cutting tool insert shape; ande) sintering the cutting tool insert shape using a pressure assisted sintering technique to form a sintered cutting tool insert, and in situ forming at least one secondary crystalline phase comprising at least one carbide, nitride, carbonitride or silicide of niobium, tantalum or mixtures thereof which is nucleated from an intergrannular phase during sintering.