Microstructure Investigation, Hot Tensile and Hot Corrosion of IN600 to Nimonic 75 heterogeneous Connection in Spot Welding

Abstract

Nimonic 75 and Inconel 600 alloys are the Nickel-based superalloys which are used in manufacturing gas turbine components. In the current research, a superalloy Ni-based Nimonic sheet and Inconel 600 were used, joint by resistant spot welded (RSW) machine at currents of 2, 4, and 6 kA, pressure of 5 and 7 bar, and times of 0.6, 0.9 and 1.2. Non- destructive inception methods and light and scanning electron method (SEM) and light optic microscope (LOM) were used to evaluate joints' quality. Shear and micro-hardness test was used to check the mechanical properties of the joint. The findings indicate that the most appropriate welding connection of inhomogeneous points at the current of 4 kA was the holding time 0.9 second and electrode force 7bar. The analysis of microstructure consisted of 3 welding zones which are affected by heat and the base metal. The warm corrosion scanning microscope test results at 600 °C and 800 hours confirmed that the existence of a chromium oxide layer on the surface of the superalloy, which has the main role in protecting the piece in the output temperature.