Metallurgical and mechanical properties of hydrogen charged carbide-free bainitic weld metals

Abstract

Hydrogen embrittlement is a major concern during the welding of high-strength steels. The susceptibility of the welds to hydrogen embrittlement increases with increase in weld strength. The ever-increasing demand to increase the strength of steels necessitates the development of novel welding procedures and fillers to produce welds of high strength and with resistance to hydrogen embrittlement. In this current work, the susceptibility of carbide-free bainitic weld metals to hydrogen embrittlement is studied with varying volume fractions of constituent phases. Using three different weld metal compositions, six different weld metal microstructures of carbide-free bainite were generated. The hydrogen saturation behaviour of the various weld metals was studied by cathodic electrolytic charging and subsequent diffusible hydrogen measurements by the hot extraction method. Tensile tests were conducted on various weld metals with and without hydrogen charging to evaluate their susceptibility to hydrogen embrittlement. The results show that the carbide-free bainite weld metals are highly resistant to hydrogen embrittlement despite their very high strength.