Influence of high temperature diffusion bonding process parameters on mechanical and metallurgical characteristics of nickel superalloy to martensitic stainless steel.

Abstract

Welding of dissimilar metals is challenging because of the formation of microfissuring, strain age cracking and brittle intermetallic compounds. The above-said problems can be avoided by controlled heating and cooling rates and the formation of beneficial intermetallic layers in the joint interface using solid-state welding techniques such as diffusion bonding. This study investigates, the effect of diffusion bonding process parameters of dissimilar metals (AISI 410 martensitic stainless steel and nickel [Su 718] based superalloy). Fifteen joints were fabricated using different levels of bonding temperature (920-1,000°C), bonding pressure (10-18 MPa) and holding time (30-90 min). From this investigation, it is identified that joints fabricated at bonding temperature 980°C, bonding pressure 16 MPa and holding time 75 min yielded an extreme tensile strength (263 MPa) and hardness (450 HV) compared to the other joints. The tensile properties of the welded joints were assessed and associated with the microstructures. Optical Microscopy (OM), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) analysis were used to estimate the metallurgical characteristics of the weldment. The EDS examination was supported out to analyses the interface composition and to decide the composition at the interface. Furthermore, a lot of δ phase precipitates were likewise found in the bonded region.