Nano-Indentation Creep Behavior of the Vacuum Electron Beam Weldment of 12Cr10Co3W2MoNiVNbNB Heat Resistant Steel

Abstract

Creep behavior of the weldment of a new type of martensitic heat-resistant steel 12Cr10Co3W2MoNiVNbNB joined with vacuum electron beam welding is studied employing nano-indentation technique at room temperature. Different load-displacement curves are obtained for base metal, heat affected zone (HAZ) and weld metal of the welded joint. The creep displacement exhibits a sharp rise at first, then the creep rate continuously decreases with time, and is approaching zero at late steady-state creep. The creep rate of the weld is smaller than HAZ, than base metal for late creep stage. Overall, the indention stress decreases with increasing dwelling time for all the regions, and weld metal yields the greatest indention stress while the base metal has the lowest value. Weld metal exhibits the smallest creep strain rate sensitivity value, indicating it has the best room temperature creep resistance, probably due to the newly formed wide lath martensite. The weldment yields various microstructure for base metal, HAZ and weld metal, and wider martensite laths with a high dislocation density are found in the weld seam.