Effect of W on Creep Properties of Martensitic Heat Resistant HT9M Steels

摘要

Effect of W on creep properties of martensiticheat resistant HT9M steel have been investigated at 600 and 650deg C. The creep rupture strength of W added HT9M steel washigher than that of HT9M steel. The addition of W decreased theself-diffusion rate of iron atom and delayed the microstructuraldegradation during creep. As seen in dispersion-strengthenedalloys, high stress exponent, n, and activation energy, Q_c, arefound in these steels. During creep deformation, formation ofsubgrain, growth and agglomeration of precipitates andprecipitation of Laves phase occurred. These microstructuralchanges made the steels soften. When the stress was applied,hardness values were abruptly decreased at an early stage andremained constant with time. The degree of softening of Wadded HT9M steel was less than that of HT9M. But when thestress was not applied, the decrease of hardness value was notoccurred in both steels.