Effect of W, Nb, and V Alloy Elements on the Creep Strength of Low Carbon 1 1/4C-1/2Mo Weld Metal

摘要

Modified Cr-Mo filler metals were developed with elemental combinations of W-Nb-V, Nb-V, and W only. A standard low carbon Cr-MO weld metal was used for comparison. Creep stress rupture tests show that the combination of alloy elements, W, Nb, and V, provides the optimum contributions for improvement in creep properties. The enhanced properties of the modified weld metals are far superior to standard 1 1/4Cr-1/2Mo weld metal and base metal. A creep strengthening mechanism for the W-Nb-V modified weld metal is proposed based on the creep results, carbide evolution sequence, and carbide morphology corresponding to the postweld heat treatment (PWHT) condition. These W-Nb-V modified Cr-Mo filler metals can be more readily applied to weldment fabrication and repair because of a low carbon content and high creep resistance in elevated temperature service.