Improvement of corrosion resistance of SS316L manufactured by selective laser melting through subcritical annealing

The effect of heat treatment on pitting-corrosion resistance of 316 L stainless steel manufactured via selective laser melting (SLM) was investigated. The result shows that both pitting-corrosion resistance and mechanical properties under Subcritical-temperature heat treatment (950 degrees C) are better than 1100 degrees C and as-received. For as received samples, the most prone to pitting corrosion is melt-pool boundary (MPB). Subcritical-temperature heat treatment not only eliminates MPBs and high-density dislocation but also retains advantages of inclusion nanocrystallisation, cellular substructure. And recrystallisation occurs during 1100 degrees C heat treatment significantly reduces low-angle grain-boundary density and increases segregation and re-precipitation, which weakens corrosion resistance and mechanical properties.