Investigations on hardfacing and wear characteristics of nickel-based Inconel 625 overlaid welds over AISI 347 pipe

Abstract

The article focuses on investigating the effect of process parameters and wear behaviour of overlaid welds. Gas metal arc (GMAW) hardfacing is widely employed for repairing and to improve the performance of the engineering components. In this research, hardfacing is performed in the range of 130–150 A with filler wire of Inconel alloy (IN625) on the AISI 347 substrate. Successful overlaid welds were made for 150 A current at a speed of 250 mm/min and observed a continuous and even layer on the substrate. A primary current of 150 A or more can be used to overlay a uniform and continuous layer to the substrate by varying the welding speed. Higher contact angle and lower dilution were noticed at higher current and higher overlaying speeds. The increase in primary current increased the dilution and reduced the contact angle with lower bead width. In-depth microstructural examination exposed defect-free Inconel 625 hardfaced overlays with better metallurgical bonding at the interface. The overlay weld thickness varied in the range of 1.50–2.62 mm on the substrate. The hardfaced layers contain dendritic and interdendritic precipitates of Nb along the AISI 347 substrate. The intermetallic precipitates in the upper region of the overlaid weld are combined with columnar dendrites to form the Laves and (Nb, Ti) C phases. The EDS plots show the lower concentration of Fe in the IN625 overlay welds. EDS examination shows the Fe elemental dispersion and increase in the wt% of Fe in the partially melted zone of the substrate. The as-deposited overlay consists of Ni3Si, M23C6 and Ni3B phases. The micro-Vickers hardness of the hardfaced layers revealed the presence of HAZ in the substrate by GMAW process. At the applied load of 90 N, The wear rate increased with the increase in applied load on the overlaid welds from 20 to 90 N. The wear trend varies with applied load and wear time. The successfully deposited overlay welds can be suitable for worn surfaces and engineering applications to protect the stainless steels.