Impact of Selective Laser Melting Additive Manufacturing on the High Temperature Behavior of AISI 316L Austenitic Stainless Steel

Additive manufacturing allows production of complex geometries or customized designs that are difficult or impossible to fabricate by conventional means. However, these components have hardly ever been tested in severe conditions corresponding to real functioning at high temperature. The high temperature oxidation of AISI 316L stainless steel additively manufactured by selective laser melting (SLM) has been studied for 100 h at temperatures between 700 and 1000 degrees C in dry air and compared to that of wrought samples. Thermogravimetric analyses showed slower kinetics for SLM samples than for conventional coupons. In addition, SLM samples exhibit parabolic kinetics for all the studied temperatures, while conventional coupons present complete laws above 800 degrees C. Parabolic constant rate determined for 900 degrees C oxidation is one order of magnitude lower for SLM samples (1.73.10(-13) g(2) cm(-4) s(-1)) than for wrought coupons (1.54.10(-12) g(2) cm(-4) s(-1)). The resulting activation energy values confirm the better behavior of SLM alloys, in agreement with the formation at their surface of protective chromia Cr2O3. In contrast, additional formation of non-protective iron oxides was observed above 800 degrees C for the wrought samples. The different behavior could be explained by Cr depletion at the surface of conventional alloy, whereas Cr supply was still insured in the case of SLM material.