Tsuneo Tatsuno

Behavior of Nitrogen Absorption into High Speed Tool Steel Powders

Behavior of nitrogen absorption into gas atomized high speed tool steel powders has been studied by using thermo-balance in nitrogen atmosphere from 950°C to 1195°C.As the results, it has become clear that the absorbed nitrogen contents of high speed tool steel powders are in proportion to vanadium contents of the powders and the nitrogen absorbed exists as vanadium carbonitrides in the powders. Also, the nitrogen contents of the powder are not dependent on particle size, but on nitriding temperature. And the saturated nitrogen contents are higher at lower temperature.Nitrogen absorption rate into the powders is faster as the particle is finer and nitriding temperature higher.It was found that the rate-determining process of nitrogen absorption into the powders is the reaction of nitrogen molecule dissociation to atomic nitrogen on the particle surface.