Revealing the role of W in the microstructure, hardness and weldabilites of new developed Ni-xW-6Cr alloys

Abstract

Ni-xW-6Cr alloy is candidate structural material for advanced high temperature reactors due to the excellent high temperature mechanical properties and corrosion resistance to molten salts. However, high tungsten content adversely affects the weldability. In this work, Variable restraint test was carried out on Ni–W (5%∼35%)-6Cr alloys, microstructure, mechanical properties and weldability were studied. Results show that the increase of W content significantly improved the lattice size, grain size and hardness of the alloy. The hardness of weld metal is obviously weaker than that of base metal after welding. Moreover, higher W content decreased the weldabilities of Ni-xW-6Cr alloy. The solidification cracks occurred in the weld metal when the tungsten content exceeds 20 wt%. The stress concentration tended to occur at the solidification grain boundaries and promoted cracks to initiate and propagate along the solidification grain boundaries.