Journal of Welding Science

In this research, the effect of bonding temperature on the microstructure and mechanical properties of Inconel 939 super alloy by transient liquid phase bonding method. For this purpose, the middle layer of MBF20 with a thickness of 50 microns and three temperatures of 1060 °C, 1120 °C, 1180 °C and a time of 45 minutes have been used. In order to evaluate the microstructure, a scanning electron microscope equipped with an elemental analysis system has been used. Vickers hardness test and shear strength test have been used to evaluate the mechanical properties. The research findings showed that with increasing temperature from 1060 °C to 1120 °C, the width of the athermal solidification zonedecreased from 38µm to 35µm and with increasing temperature at 1180 °C, the athermal solidification zone was completely removed and isothermal solidification zone was replaced. In addition, with increasing temperature, the hardness in the joint center decreases and the shear strength increases.

Repair welding of nickel-based superalloy Inconel 939, which was under working conditions of 100,000 hours, was performed by gas tungsten arc welding using Inconel 617 filler metal. The main objective of this study is to investigate and analyze the challenges during welding such as irregular distribution of primary MC carbides and crack formation in the heat-affected zone, and also to investigate the effect of post-welding heat treatment cycle on the microstructure and hardness of different weld zones. During welding, a crack of 91 micrometers length was observed in the heat affected zone, which due to the presence of a liquation film and accumulation of carbides around the crack, the crack was categorized as a liquation crack. Then, due to post-welding heat treatment, improvement of microstructural characteristics and hardness of the weld zone, partial melted zone, and heat-affected zone was observed, which resulted in homogenization of the hardness profile of the weld. It was observed that post-welding heat treatment caused the crack formed during welding to grow and spread to reach a length of 386 micrometers, which was classified as a strain-aging crack due to its formation and growth during post-welding heat treatment.