Tushar M. Sonar
Department of Welding Engineering, Institute of Engineering and Technology, South Ural State University, Chelyabinsk, Russia.
Title: Welding of Nickel based superalloy for gas turbine engine applications
Biography
Biography: Tushar M. Sonar
Abstract
Statement of the Problem: Inconel 718 is a nickel-ferrous-chromium based superalloy extensively used in the industrial sector at elevated temperature up to 650oC owing to its better mechanical properties and weldability. However, it is amenable to some metallurgical problems during welding such as constitutional segregation and consequential laves phase formation in fusion zone (FZ) which severely deteriorates the service performance of Inconel 718 joints. This alloy also reveals extreme tendency to microfissuring in heat affected zone (HAZ) owing to the eutectic phases and carbides developed at the grain boundaries. It causes the premature failure of welded aero-engine components. Gas Tungsten Arc Welding (GTAW) process is comprehensively employed for welding of Inconel 718 to produce high-quality joints. However, the high heat input and lower joint penetration associated with wider bell-shaped arc column principally constrains its applications and employability in making the highly efficient joint. The laves phase formation and HAZ microfissuring can be mitigated by lowering the heat input and increasing the rate of cooling. The electron beam (EBW) and laser beam (LBW) welding have shown significant influence on minimizing the laves phase formation but they are susceptible to porosity related defects and liquation cracking owing to the rapid rate of cooling. This paper provides an overview of the weldability studies on Inconel 718 alloy. The physical metallurgy of Inconel 718 alloy is explained briefly. The effect of welding processes (GTAW, EBW and LBW) on microstructural characteristics, tensile properties, hardness, hot tensile, stress rupture and hot corrosion of Inconel 718 joints is reported and discussed. Keywords: Inconel 718, Segregation, Laves phase, Microstructural Characteristics, Mechanical Properties, Post weld heat treatment.