Effect of Vanadium and Carbon Content on the Sinterability of Water Atomised High Speed Steel Powders

Abstract

This paper presents the results of an investigation into the sintering behaviour of three vanadium enriched variants of T42 high-speed steel. Powders were prepared by water atomization with vanadium and carbon contents of 6-8 wt% and 2.2 -2.7 wt%, respectively. These were annealed, die pressed and sintered in vacuum. All three alloys were sintered to full density giving "as -sintered" microstructures comprising globular MC carbides dispersed in a martensitic matrix. Optimum sintering temperatures were in the range 1240 -1250ºC with lower optimum temperatures associated with higher carbon levels. Sintering characteristics are correlated with phase diagrams calculated using ThermoCalc™ software and TCFe2000 database. The implications for the design of sinterable vanadium containing high-speed steels are discussed. Introduction: Supersolidus liquid phase sintering (SLPS) was demonstrated by Wright[1] as being the processes through which sintering of high speed steels (HSS) is carried out. In SLPS, prealloyed powders are heated to a temperature intermediate between the solidus and liquidus, Fig. 1. This method has been applied to a number of systems [2,3,4] including HSS [5,6,7,8,9].