Fatigue and microstructural study of a 316L austenitic stainless steel marine component produced by Wire Arc Additive Manufacturing (WAAM)

Sammanfattning: In this study, the fatigue- and fracture properties and microstructure of a marine component of austenitic stainless steel 316L manufactured with the novel method Wire Arc Additive Manufacturing were investigated and compared with data from literature. The purpose was to find a critical flaw size in the material related to its fatigue life. It was done by studying the microstructure and interpreting fatigue- and mechanical data for the marine component in empirical models related to the fatigue- and fracture properties. Fracture properties were approximated to estimate fatigue life and critical flaw size. Fatigue limit and fatigue threshold were based on hardness test data, fracture toughness, and FADs on Charpy-V impact test data. The material manufactured with Wire Arc Additive Manufacturing had superior fatigue properties than cast and rolled equivalents and performed better in the fatigue test than recommendations for austenitic stainless steel in a seawater environment from the British Standard 7910:2019. Due to the conservative model's fatigue limit and fatigue threshold, the results are conservative. The reason for that could be the crack closure properties of the material. The results for fracture toughness are lower than the literature data. This is most likely due to conservative models based on Charpy-V impact test data. The most important properties of the fatigue life are the fatigue limit and the fatigue threshold due to their relationship with crack growth. Testing the lifetime of the component in seawater is complex and time-consuming due to the corrosion and the need for low test frequency.