Some studies on nickel based Inconel 625 hard overlays on AISI 316L plate by gas metal arc welding based hardfacing process

Abstract

The aim of the study was to examine the characteristics of Inconel 625 hard overlays over AISI 316L used for oil and gas industry applications. Weaving technique was adopted using robotic gas metal arc welding (GMAW) process in this study to reduce the dilution % and contact angle. Multiple overlapped beads were fabricated with a welding current of 120 Amps, welding speed of 250 mm/min with sinewave weaving technique. The hard overlays were then examined to expose the microstructural variation and mechanical integrity. In addition, reciprocating wear test and three-body abrasion tests were performed to study the wear characteristics. Microstructural results showed the existence of precipitates rich in Mo and Nb dispersed in the interdendritic regions with a dendritic structure. Hardfaced overlay and interface samples showed an increase of 17.8% and 3.7% respectively in ultimate tensile strength than the substrate material. Microhardness test exhibited intended results which follow an increasing trend from substrate to the overlay with an average of 246.02 HV0.5 at the overlay region and 184.94 HV0.5 on the substrate zone. Wear test results revealed excellent wear resistance of the hardfaced samples in comparison with substrate specimens. Co-efficient of friction (CoF) of hardfaced samples were 0.16 and 0.12 while the CoF of substrate specimen were 0.25 and 0.53 at room temperature and 180 °C respectively in ball on flat reciprocating wear test. Specific wear rate of hardfaced samples during the three-body abrasion test at 50 N and 130 N load decreased by ⁓39% in comparison with substrate. The surfaces of the worn samples from the wear test were characterized by SEM wear tracks and Energy Dispersive Spectroscopy analysis.