Structure and its defects in additive manufacturing of stainless steels by laser melting and electric arc surfacing

Abstract

Currently, there is an active development and study of additive technologies. Metal 3D printing makes it possible to obtain parts and structures of complex configuration using a minimum of shaping operations, which can lead to a reduction in overall cost of the resulting products. In this paper, we studied the structure formation in manufacture of products made of stainless steels 10Cr12Ni10Ti (analogue of AISI 321) and 08Cr18Ni9 (analogue of AISI 304) by additive methods – SLM (Selective Laser Melting) and WAAM (Wire Arc Additive Manufacturing). In the course of microstructural analysis, it was found that during the manufacture of products using SLM technology, small austenitic grains oriented in the direction of heat removal are formed, and with WAAM method, austenite is formed mainly in form of dendrites. It is shown that porosity is formed during manufacture of the samples by SLM method, which is associated with non-melting of individual powder particles. When implementing additive manufacturing by WAAM (electric arc surfacing), there is no increased porosity. In the course of the study, a new defect of the structure formed during the manufacture of products by both methods was revealed – formation of interface boundaries between layers, which is associated with the technology of additive manufacturing itself. When manufacturing a WAAM product, it manifests itself more clearly than when obtaining metal by SLM. Boundaries of the surfacing rollers in the manufacture of products by SLM accumulate various intermetallides and structural defects more intensively, relative to WAAM. As a result of the small relative volume of one surfacing roller, compared with WAAM, accumulation of these defects and intermetallides can act as an effective barrier during movement of dislocations, which can lead to an increase in the strength properties of products.