A study on effect of filler metals and heat input on weldability of inconel 617 and inconel 718 alloys and improvement of weldability through ultrasonic vibration

Abstract

Two important nickel base alloys that are used for high temperature applications are Inconel 617 and Inconel 718. Inconel 617 is a solid solution strengthened nickel alloy with chromium, cobalt and molybdenum as the main alloying elements. This alloy has a good combination of high temperature strength, corrosion resistance and oxidation resistance. Inconel 718 is an age hardenable nickel alloy with chromium, iron, niobium and molybdenum as the main alloying elements. This alloy has high strength and corrosion resistance and is used for high temperature applications upto 7000C. Hot cracking is an important metallurgical problem in arc welding of many nickel base alloys. Inconel 617 and Inconel 718 alloys are reported to be susceptible for hot cracking during arc welding. Hot cracking, occurring both in the weld metal and in the heat affected zone near the fusion line (partially melted zone), is caused by segregation of certain low melting constituents at the grain boundaries. Hot cracking increases with grain coarsening and decreases with grain refinement. Many techniques have been attempted to promote grain refinement and reducing the low melting constituents during solidification. In welding of nickel alloys, certain low melting constituents that cause hot cracking during solidification can be controlled by adjusting the composition of the weld metal such that the undesirable constituents are avoided. Hot cracking can also be controlled by appropriate choice of weld newlinethermal cycles. In the present work, an attempt is made to study the effect of various filler metals on hot cracking during welding of the two nickel base alloys, Inconel 617 and Inconel 718. The study also attempts to study the effect of heat input on hot cracking in welding of the two nickel base alloys. newline newline