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, 4-2wt-%V) is analysed as a function of the nitrogen pressure in the sintering atmosphere. Uniaxially pressed compacts were sintered to full density (>98%TD) under different N2 atmospheres in a range of pressures from vacuum to 8 bar. It is observed that the optimum sintering temperature (OST) depends on the absorbed nitrogen and is as low as 1050°C when the nitrogen content in the steel is l.2wt-%. The absorbed nitrogen affects not only the OST but also the matrix and carbides composition and the phases present after sintering. Compared with other powders processed under the same conditions, it is shown that the amount of absorbed nitrogen depends not only on the nitrogen partial pressure in the sintering atmosphere but also on the amount of vanadium and carbon and even on the heating rate. Hardness, fracture toughness, and fracture strength values are reported after heat treatment.