Patent ID: 6863963

Claim:
A silicon nitride member comprising a substrate formed by sintering a silicon nitride material, and a hard film comprising a hard component selected from the group consisting of Al 2 O 3 , TiCN, TiN and TiC formed on a surface of said substrate, said silicon nitride member characterized in that: when the strength of said substrate measured before said substrate is coated with said hard film is taken as 100%, the strength of said silicon nitride member measured after said substrate is coated with said hard film is 70% to 95%, and when used to cut plain cast iron at a cutting speed of 100 m/min, a feed rate of 0.1 mm/rev, a depth of cut of 1.0 mm and a cutting time of 60 min, the silicon nitride member exhibits flank wear in an amount of not greater than 0.2 mm and notch wear in an amount of not greater than 0.22 mm.