Laves Phase Formation and Segregation of Nb in Ni–Cr–Mo Superalloy over 316L by Hot Wire (HW) TIG Cladding Process

The Ni-based alloys are widely used in power plant components such as boiler and piping systems that require good creep strength and resistance to corrosion. The present study focuses on metallurgical and mechanical properties of Ni–Cr–Mo (ERNiCrMo-3) alloy cladded over 316L plate by hot wire TIG process. This alloy is prone to microfissuring and also reduced corrosion resistance due to microstructural changes caused by weld solidification. The microstructure and phasic characterization were identified using scanning electron microscopy and X-ray diffraction techniques. From the microstructural observation, it was observed that Nb present in Ni–Cr–Mo alloy tends to segregate during solidification of weld thereby promoting the Nb-rich Laves phase formation. The growth of dendrites enhanced the segregation of Nb. The coarse dendritic microstructure was due to the effect of high heat input that decreases solidification rate near the interface zone. Dimples and quasi-cleavage fracture morphology was observed on the fractured samples of the tensile test. The resistance to corrosion was evaluated using potentiodynamic polarization method using 3.5 wt% NaCl solution. The results confirmed that Ni–Cr–Mo alloy acts as an efficient clad for 316L substrate from corrosion attack.