The Impact Toughness of Nd:YAG Laser-Welded GTD-111 Superalloy Joints

The aim of this study was to investigate the impact behavior of GTD-111 superalloy in the temperature range of 25 to 850 °C. The results showed that the highest impact toughness was obtained at 600 °C. However, when the specimen is subjected to an impact test at 750 °C, the lowest impact toughness is obtained. As the test temperature rises from 750 to 850 °C, the impact toughness increases again. Microscopic observations of the fracture cross section showed that most of the cracks originated from MC carbides due to the high stress concentration in these sites, which resulted in low impact toughness at 25 °C. Destruction at 600 °C was a dutile failure, resulting in the formation of dimples that acted as energy absorption sites during impact testing. The reason for the decrease in impact toughness at 750 °C is also the increase in the strength of the alloy due to the strain hardness and the accumulation of dislocations. The results of the tensile test at the above temperature also confirm this.