| 摘要 |
PURPOSE:To obtain a coated sintered hard alloy excellent in heat shock resistance and tenacity, by a method wherein specific sintered hard alloy parts is held under heating in an atmosphere of which N2 partial pressure is adjusted and films of TiC and Al2O3 are laminated on the surface of the heated hard alloy parts to improve the bonding strength thereof. CONSTITUTION:Sintered hard alloy parts containing WC and bonded by a ferrous metal is preliminarily held in an atmosphere of which partial pressure is 1-700 Torr at 1,200-1,600 deg.C for 10min-5hr. By this heat treatment, the substrate surface is enriched so as to adjust the Co content at a part of a least 1mu depth from the surface of sintered hard alloy to 40% or less lower than that in the interior of the hard alloy and to adjust the proportion of the B-1 type solid solution to 40-80vol%. In the next step, on the surface of this parts, a composite film consisting a TiC layer with a thickness of 0.2-6mum as a lower layer and an Al2O3 layer with a thickness of 1-5mum as an upper layer are formed. By this method, the generation of an eta phase is prevented and a coated sintered hard alloy rich in heat shock resistance and mechanical shock resistance is obtained. |
