Effect of Carbon Additions on Sintering Characteristics and Microstructure of BT42 High Speed Steel

Abstract

The isochronal vacuum sintering behaviour of BT42 grade high speed steel after cold compaction of annealed, water atomized powder is reported. Densities of the order of 99% theoretical were readily achieved. For the as received powder the sintering temperature range was 1245–1260°C. The effect of adding nominal 0·01% elemental carbon was negligible. For 0·1%C addition densification commenced at a lower temperature and the sintering range was reduced to 1230–1250°C. The addition of carbon had no deleterious effect on the microstructure. The primary carbides present in the microstructure (compositions, excluding carbon, in weight per cent) were ∼9%M₆C (4Co–4Cr–28Fe–14Mo–3V–47W), ∼13%MC (lCo–4Cr–4Fe–15Mo–41V–35W), and M₃C (cemenite). When the specimens were oversintered by ∼ 20 K grain boundary eutectic carbides (4Co–14Cr–40Fe–20Mo–6V–16W) were also detected. PM/0445