Inconel 625 Coatings on AISI 304 Steel using Laser Cladding: Microstructure and Hardness

Nickel-base super alloys such as Inconel 625 are preferred in high-temperature and corrosive environments. Since Inconel 625 is expensive and often difficult to machine, it is advantageous to deposit a protective coating of this alloy on a less costly and easily machinable substrate material such as stainless steel. In the present work, coatings were produced on AISI 304 steel substrate by depositing Inconel 625 powder using the laser cladding technique. As-received powder particles of Inconel 625 alloy were characterized using X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM). After laser cladding, it becomes important to carry out the microstructural analysis of the cross-sectional areas of the coating and the substrate/coating interface region, for further understanding of the structure-property correlations. In this study, the microstructural features of the coatings and substrate/coating interface were examined using an FESEM equipped with X-ray elemental analysis. The phase analysis of the coating was carried out using XRD. In the coating region, the growth of planar, cellular, columnar dendritic, and equiaxed grains was noticed. It was observed that small amounts of Laves phase were precipitated. Furthermore, the laser-clad Inconel 625 coating showed superior microhardness over the stainless steel substrate.