Optimizing the corrosion resistance and hardness of TA31 alloy by selective laser melting

In this work, SLM TA31 alloys were fabricated by varying the laser scanning speed while maintaining a constant laser power. Two well-formed SLM TA31 alloys were selected for detailed investigation of their corrosion resistance and hardness, with rolled TA31 alloys used as a benchmark for comparison. The results showed that the SLM TA31 alloy fabricated at a scanning speed of 900 mm/s exhibited the best corrosion resistance and improved hardness, while that fabricated at 1000 mm/s showed the poorest corrosion resistance but still had enhanced hardness compared to the rolled alloy. The observed variations in corrosion resistance among the SLM TA31 alloys were attributed to the combined influence of the metastable martensite α ′ phase content and the variations in grain boundary density within their microstructures. The beneficial effect of grain refinement leads to an increase in the number of grain boundaries and facilitates the nucleation of passive films, thereby overcoming the detrimental effects of the metastable α ′ phase. This results in SLM TA31−900 alloy having excellent corrosion resistance compared to rolled TA31 alloy. The improved hardness was primarily due to grain refinement and the formation of harder martensite α '/ α phase.