Effect of Heat Treatment on Microstructure and Mechanical Properties of 15-5 pH Stainless Steel for Fastener Applications

15-5PH stainless steel is widely used in the aerospace industry, from precision fuse pins to forged products, due to its various high-performance properties. However, there is little systematic evaluation of heat treatment responses, especially at ultra-high temperatures above 650°C (1200°F). The objective of this work was to evaluate the mechanical and microstructural properties of 15-5 PH stainless steel at various heat treatments. Multiple heat treatment parameters were tested. The samples tested had varied chemical compositions because they were from different vendors. The experimental work included multiple aging temperatures, time, heating rates, and the effects of multiple aging treatments. A total of 38 different heat treatments were conducted on these specimens. There was a linear correlation between hardness and ultimate and yield strength. Optical microscopy showed martensitic structures with very fine grains in all the tested samples. Scanning Electron Microscope (SEM) images showed ductile fracture in all the samples.