Effects of process parameters on the high temperature strength of 17-4PH stainless steel produced by selective laser melting

In this study, the effects of process parameters on the high temperature strength of 17-4PH stainless steel manufactured by selective laser melting (SLM) were investigated. Nine rectangular block specimens were fabricated with various process parameters. Small punch (SP) tests were conducted at 425 degrees C four times for each rectangular block specimens. The average maximum SP loads were measured from the tests. The fracture surfaces of SP-tested specimens were also examined. Un-melted powder was observed on the fracture surface of the specimen with the lowest average maximum SP load value, which could give rise to local cracking. Analysis of the microstructures showed that the retained austenite and amount of pore defects were the main factors that could affect SP test results. Regression surface methodology (RSM) models was applied to predict the maximum strength as a function of laser scan speed and energy density. Results showed that the energy density level of 64.29 J/mm(3)and a scan speed higher than 1884 mm/s are recommended for fabricating SLM parts in the shortest time without losing material strength and with minimum metallurgical defects.