EFFECT OF W ON MECHANICAL PROPERTIES OF 12%Cr HEAT-RESISTANT STEEL

The effect of W on mechanical properties of 12% Cr-W-V-Nb heat resistant steel at hightemperatures and room temperature is reported.The experimental results indicated that if theW content was about 2.2—3.0 wt-%,there was no obviously change of R.T.tensile strength,but impact toughness decreased with the rise of W content.On the other hand,the increase ofW content enhanced the short time stress rupture strength,but did not for the long time one.The increase of W have two effects on the precipitation behavior,promoting Laves formationof type Fe_2W,increasing the precipitated phase amount and speeding up the coarsening pro-cess of precipitated phase at high temperatures.The effect of W on the mechanical propertiesis closely associated with precipitation behaviors.When the rupture life is short,there has noenough time to coarsen the precipitated phases,so the increase of precipitated phases results instrengthening effect,i.e.the W increases the high temperature strength.After prolonged expo-sure,the evident coarsening took plaee,that decreased the effect of precipitation.