Additive manufacturing of high-strength weathering steel parts fabricated by gas tungsten arc: Microstructure and mechanical properties

This study focuses on microstructure and mechanical properties as a function of location in additively manufactured high-strength weathering steel components using gas tungsten arc as the heat source. Variations of microstructure and mechanical properties in various locations are presented and analysed. The as-deposited high-strength weathering steel is composed of columnar grain morphology with proeutectoid ferrite, acicular ferrite, side plate ferrite and a small amount of pearlite microstructure in the top region, equiaxed grains with ferrite and pearlite in the middle region, and columnar grains in the near-substrate region with the microstructure similar to that in the top region. There exist obvious layer bands in the middle region, and the forming mechanism of the bands is addressed. Microhardness measurement and tensile strength testing indicate obvious changes in different regions, depending on location and direction of testing specimens. The microhardness in the middle region is inferior to that in both near-substrate and top regions. The ultimate tensile strengths in the travel and deposition height directions are approximately 553 and 506 MPa, respectively. Different locations exhibit heterogeneous tensile strength and elongation due to various microstructures and boundaries. The results indicate the feasibility to fabricate high-strength weathering steel components with good tensile properties using gas tungsten arc-based additive manufacturing.