Liquid Phase Sintering of Various High Speed Steels with Copper-Phosphorus Addition

Abstract

High speed steel powders are conventionally pressed and vacuum sintered to near full density at temperatures of 1250–1350°C. By adding Cu-P alloy powders this sintering temperature is considerably reduced in a wide range of different high speed steels and full density can be achieved at sintering temperatures well within the capabilities of continuous mesh belt furnaces. The application of high speed steels to wear resistant components requiring high volume production could be enhanced by this process. The formation of a liquid phase during sintering was confirmed and essentially two types of sintering behaviour occur, depending on the molybdenum/tungsten content of the high speed steel. Liquid phase formed by a low melting point phosphide-carbide eutectic reaction promotes densification by particle rearrangement in molybdenum rich alloys but this mechanism changes, to become dominated by solution-reprecipitation, in tungsten rich alloys. PM/0550