Strengthening of additively manufactured tungsten by use of hydrogen in argon shielding gas

Additively manufactured tungsten was printed in atmospheres of pure argon and argon-3% hydrogen and compared on the basis of microstructure, chemical composition, and three point bend tests. The argon-3% hydrogen atmosphere refined microstructure and markedly increased flexural strength, achieving a maximum of 985 MPa. Chemical composition analysis revealed high levels of oxygen in argon-3% hydrogen parts compared to pure argon. It is proposed that the argon-3% hydrogen atmosphere aided the formation of tungsten oxides and slowed their sublimation. These oxides likely led to grain refinement by grain boundary pinning. The grain refinement produced a ribbon-like microstructure which resulted in higher strength transgranular fracture