High Energy Density Welding of IN792 Ds Superalloy

Abstract

Ni base superalloys are commonly employed in the industrial fields of aerospace, automotive and energy production due to their excellent mechanical properties and corrosion resistance at high temperature. Superficial defects and cracks may occur during both manufacturing process of components and their service life. High energy density welding techniques, electron beam (EBW) and laser beam (LBW) welding, can be used to create efficient repairs. Joints, obtained by EBW and LBW of IN792 directionally solidified (DS) superalloy, have been investigated to determine the presence of defects, and evaluate the mechanical properties related to specific microstructural features. The results showed that a pre-heating temperature (PHT) higher than 200 °C is always necessary to prevent the formation of hot cracks in the molten zone (MZ) and heat affected zone (HAZ). The process parameters have been optimized to get a good quality of the seams (lack of macro-defects, a good penetration depth and width). Some preliminary test of post-welding heat treatments (PWHTs) have been investigated to homogenize as far as possible the microstructure and the mechanical properties across the seams. The results obtained by the two techniques, EBW and LBW, have been compared and discussed.