High cycle fatigue behaviour of Inconel 625 weld overlay on AISI 316L plate

Abstract

In this work, the high cycle fatigue (HCF) investigation was performed on Gas metal arc welding (GMAW) based Inconel 625 (IN625) hardfaced overlays in as-deposited condition. Tensile test and microstructural characterization were performed along with HCF analysis. The microstructure of the weld overlay was characterized with equiaxed, columnar and randomly oriented dendritic microstructures, these dendrites imparts improved mechanical properties. Higher amount of high angle grain boundaries (HAGBs) fraction at the IN625 section has direct effect on improving the toughness and strength of the overlay material. Monotonic tensile results indicate 5% increase in Ultimate tensile strength (UTS), 21% increase in Yield strength (YS) and 32% decrease in elongation to failure (PE) on hardfaced sample than the substrate. Fatigue strength was considered 143 MPa and 119 MPa for hardfaced and substrate samples respectively after sustaining infinite number of cycles. Fatigue resistance of hardfaced material was remarkable due to the presence of equiaxed dendrites and defect free overlays. Smooth crack growth area was noticed for the samples failed at higher number of cycles, expressing low stress-levels. Specifically, the fracture surfaces evidenced micro voids, riverine traces and dimples at the fracture point, which confirms the ductile failure.