SINTERABILITY OF POWDER-METALLURGY TOOL STEELS PRODUCED WITH THE APPLICATION OF HEAT-TIME TREATMENT OF THE MELT

Powder metallurgy tool steels prepared from the powders of gas-atomize d melts subjected to heat-time treatment were studied. Material contai ning above 1.2% carbon, in addition to tungsten and molybdenum, exhibi ted a porosity decrease of 6-12% after vacuum sintering at a temperatu re 70 degrees C lower than that of solid-phase sintering. The increase d sinterability of the alloys was related to the presence of a high, c lose to eutectic, carbon concentration at the surface of fine powder p articles (principally 50-100 mu m), and is explained by the formation of liquid phase during the process of leveling the element concentrati on gradients.