Sintering of modified M35MHV HSS under diferent nitrogen pressures

The sintering behaviour of high carbon-high vanadium water atomised M35MHV HSS (1(.)8 wt-%C, 4(.)2 wt-%V) is analysed as a function of the nitrogen pr essure in the sintering atmosphere. Uniaxially pressed compacts were sinter ed to full density (greater than or equal to 98%TD) under different N-2 atm ospheres in a range of pressures from vacuum to 8 bar. It is observed that the optimum sintering temperature (OST) depends on the absorbed nitrogen an d is as low as 1050 degreesC when the nitrogen content in the steel is 1(.) 2 wt-%. The absorbed nitrogen affects not only the OST but also the matrix and carbides composition and the phases present after sintering. Compared w ith other powders processed under the same conditions, it is shown that the amount of absorbed nitrogen depends not only on the nitrogen partial press ure in the sintering atmosphere but also on the amount of vanadium and carb on and even on the heating rate. Hardness, fracture toughness, and fracture strength values are reported after heat treatment. (C) 2001 IoM Communicat ions Ltd.