Hard metal or cermet body useful as a cutter insert

摘要

A hard metal or cermet body, having a case region comprising outer layers of specified fixed or graded compositions and an innermost layer of specified graded composition, is new. A hard metal or cermet body with a hard phase of WC and/or one or more group IVa, Va and/or VIa element carbides, nitrides, carbonitrides and/or oxycarbonitrides and 3-25 wt. % of a Fe, Co and/or Ni binder phase and with a case region of layers of different compositions. The novelty is that the WC content of the hard phase is 10-96 wt. % and that: (a) an exterior layer adjacent the body surface is 2-30 microns deep and comprises a binder-free carbonitride phase; (b) an underlying middle layer is 5-150 microns thick and approaches a pure WC-Co composition; and (c) a lower most layer is 10-650 microns thick and has binder phase and group IVa and/or Va element contents which increase to the constant values at the body interior and a tungsten content which decreases to the constant value at the body interior. Independent claims are also included for the following: (i) a similar hard metal or cermet body in which all the layers have graded compositions; and (ii) a process for producing the above hard metal or cermet body.