Heat treatment-induced microstructural transformations and strengthening mechanisms in laser powder bed fusioned 15-5PH stainless steel

Abstract

This study systematically examined the effects of solution treatment-aging (ST-AT) and aging treatment alone (AT) on the microstructure, wear resistance, and mechanical properties of 15-5PH stainless steel fabricated via laser powder bed fusion. The underlying strengthening mechanisms were also analyzed. Experimental results revealed that AT samples maintained a dual-phase structure of α-martensite and γ-austenite, with partially heterogeneous layered structures. In contrast, the ST-AT samples underwent complete transformation to single α-martensite phase, characterized by flat and noodle-like martensite. Performance testing revealed a notable increase in hardness for both ST-AT and AT samples, though wear resistance slightly decreased. The ultimate tensile strength and yield strength (YS) of the AT and ST-AT sample reached 1384 MPa, 977 MPa, and 1398 MPa, 1264 MPa, respectively, accompanied by slight reductions in elongation to fracture. Dislocation strengthening accounted for 60.3% of the YS increase in ST-AT samples, with a theoretical YS of 1295 MPa closely matching experimental results.

Keywords

• Additive manufacturing
• Heat treatment
• Microstructure
• Wear performance
• Mechanical properties
• Strengthening mechanism