Structure–Property relationships of Inconel 625 Cladding on AISI 316L substrate produced by Hot Wire (HW) TIG metal deposition technique

Abstract

The high oxidation resistance Ni-based superalloy, Inconel 625 is widely used to produce engineering components. The cladding of Inconel 625 can be used for cheaper substrates, which can withstand maximum mechanical loads and extreme environments at high temperature. The main reason for using Inconel 625 in cladding, is that it can be deposited on any substrate, facilitating to work under extreme temperatures. The advantages of using cladding as a protecting layer are the significant reduction in costs when compared to using in bulk alloys. The present study investigates the microstructure of the cladding of Ni-based Inconel 625 on the 316L substrate using a preheating wire technique called Hot Wire (HW) Tungsten Inert Gas (TIG). The process parameters chosen include welding current (140, 160, 180 Amps), torch angle (60, 70, 80 degrees) and travel speed (125, 150, 175 mm min−1), with a constant voltage of 17 volts. Findings revealed that, by using optimum process parameters, the clad beads were free from porosity, with a minor geometric dilution claddings were produced. The scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD) were used in investigating the microstructural and elemental characterization. The mechanical properties of the clad beads were analyzed using Vickers microhardness indentation method. The tribological properties of the clad beads were analyzed using pin on disc wear tester. From the micrographs obtained, the cladding microstructures from topmost portion of the clad to interface boundary nearer to the substrate composed of columnar, cellular structure dendrites and coaxial structures. The formation of the austenite, carbides and Laves phases were also noticed in the clad region of Inconel 625. The minimum amount of Fe present in the clad region containing Inconel 625 clad region is confirmed through EDS curve. The clad bead shows higher microhardness due to grain refinement effect. The main factor upon which pin on disc wear mechanism depends are the applied load and wear time. Initially wearing time is minimum and applied load is 20 N, the wear mechanism becomes abrasive wear and when applied load is 90 N wear mechanism becomes adhesive in nature. Increasing the wear time, makes the wear into adhesive and applying minimum load produces oxidation wear, whereas applying high load produces fatigue wear.