Characteristics of surface layer of sintered stainless steels after remelting using GTAW method

The study presents the results of the investigations concerning the effect of remelting using gas tungsten arc welding (GTAW) process on the microstructure and selected properties of the surface layer in sintered multi-phase steels obtained from powders of 304L and 434L steels. The effect of surface treatment was evaluated based on macro- and microstructural observations, EDS analysis, X-ray phase analysis and measurements of surface roughness and microhardness. It was found that remelting of surface layer leads to elimination of open porosity and homogenization of the structure, which was confirmed by microscopic observations and microhardness tests. A cellular or mixed cellular and dendritic structure was formed in the remelted zone in the sinters. Growth of columnar crystals occurred along the direction of heat transfer. Using the energy dispersive spectroscopy (EDS), the authors found higher concentration of alloy elements in the intercellular zones compared to cell cores. X-ray analysis demonstrated that the remelting used is conducive to formation of the austenitic phase in the remelted material.