Sintered hard metal article with a binder-enriched and/or cubic carbide-depleted surface zone

摘要

A sintered hard metal article, comprising a hexagonal carbide phase, a cubic carbide phase and a metal binder phase, has a binder-enriched and/or cubic carbide-depleted surface zone which is obtained by combined nitrogen supply and vacuum sintering and which is reproduced, after machining, by vacuum heat treatment. A sintered hard metal article, consisting of a hard metal alloy of hexagonal tungsten carbide phase, a cubic mixed carbide phase of group 4a and 5a metal carbides and a Fe, Co or Ni metal or alloy binder, has a binder-enriched and/or cubic carbide-depleted surface zone obtained by: (a) producing a sintered shaped hard metal body with a binder-rich and/or carbide-depleted surface zone by a combination of nitrogen supply and vacuum sintering; (b) finish machining of the body to its final contour; and (c) reproducing the surface zone in the machined regions by vacuum heat treatment. An Independent claim is also included for reproducing a binder-rich and/or carbide-depleted surface zone on a machined sintered hard metal article by vacuum heat treatment, preferably at 600-1,300 deg C for up to 150 min. Used especially as a rim zone or gradient structured sintered hard metal tool or cutter insert.