Creep rupture Strength and microstructure were investigated for base metals and simulated HAZ specimens of 9Cr-Mo or 9Cr-W steels with V and Nb.Results obtained were as followed.(1)The 1000 deg C HAZ Specimens show minimum creep rupture strength.(2)Decrease in rupture strength in the 1000 deg C HAZ depends mainly on combined effect of grain refinement and coagulated carbides for 9Cr-1Mo type steels.(3)Substitution of W for Mo is very effective in enhancement of creep rupture strength of HAZ.(4)Weakening of the HAZ is reduced by increase in amount of carbides during aging and higher stability of carbide with higher W content for 9Cr-2W type steels.
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