A comprehensive assessment of the microstructure of heat affected zone and its influence on the mechanical properties of cladded components used in the power sector

In recent years, across the globe, several incidents of failures of mechanical components are observed in the power generation sector, nuclear industry, chemical industry, and process industry due to surface cracking. To meet such challenges, cladding of superalloys on the substrate can be done by using advanced welding processes. Although cladding improves mechanical properties, through service life delamination of the weld cladding from the substrate results in collateral damage to components as a turbine and valve failure, mainly due to complex metallurgical changes by uneven cooling and heating in the heat affected zone (HAZ) of the substrate during cladding. The HAZ can vary in severity and size depending on the composition of cladding material and substrate, heat intensity, and the cladding process. It leads to drastic changes in mechanical properties such as creep and fatigue resistance, distortion, and surface cracking. This makes it extremely crucial to learn about the microstructure characterisation of HAZ during cladding. This article provides information related to metallurgical reaction in the HAZ during the deposition of superalloy on substrate. The article aims to address major issues related to HAZ as variation of hardness profile and type of HAZ cracks. Furthermore, an intense review on the controlling approach of HAZ formation is included. Also highlighted are overall findings related to HAZ formation and its influence on metallurgical and mechanical properties, and possible future direction in the context of critical challenges that need to be catered prior to cladding. After performing a comprehensive study on HAZ formation during the cladding operation, it is observed that HAZ formation is a complex phenomenon, it is affected by various factors viz. heat input, cladding processes, properties of materials, etc. Efforts have been made to summarise all the information related to HAZ.