Effect of nitrogen on supersolidus sintering of modified M35M high speed steel

Water atomised high vanadium M35M high speed steel powders with different c arbon contents were cold compacted at 700 MPa and sintered under an N-2 ric h atmosphere. Full density specimens were obtained at temperatures between 1140 and 1105 degrees C for carbon contents between 1.8 and 2.5 wt-% respec tively. The sintering behaviour of these powder mixtures was correlated wit h dilatometric curves and phase diagram calculations made by Thermo-Gale so ftware. It is demonstrated that densification takes place above the solidus temperature, within the austenite + carbide + liquid phase field, and that nitrogen widens this region, which is responsible for increased sinterabil ity with regards to vacuum sintered high speed steel. PM/0836 (C) 1999 IoM Communications Ltd.