Correlation between microstructural gradient and microindentation properties of dissimilar weld between INCONEL 625 and Duplex Stainless Steel

摘要

Microstructure evolution and microindentation properties of dissimilar weld between Inconel 625 nickel based alloy and UNS S32205 Duplex Stainless Steel have been investigated in the current study. Samples in cross-section areas were prepared to investigate microstructure and micromechanical properties in different regions of weld using optical microscopy, scanning electron microscopy and indentation measurements. Typical solidification microstructures were observed. Secondary phases were noticed in both the weld metal and heat affected zone of Inconel 625 alloy at cellular and interdendritic region in lamellar, rod shaped and cuboidal form. These secondary phases were identified as Laves phase and carbonitrides of Nb and Ti. Mechanical properties including elastic modulus and hardness were estimated across the weld joint. The results showed that the weld metal exhibit the lowest values of hardness and elastic modulus, however the Heat Affected Zone of the stainless steel exhibit the highest values owing to high delta-ferrite amount. In-situ nanoindentation coupled with Scanning Electron Microscope was carried out in Laves phase and the matrix weld in order to evaluate nanohardness. The result showed that the nanohardness of Laves phase is too great compared to the weld matrix.