Determination of Ideal Conditions for GTD-111 Superalloy Welding Through Pre-Heating, Pre-Cold and Heat Treatment

Abstract

The objective of this research is to investigate the effect of heat treatment and pre-heating and pre-cold temperatures on hot cracks and microstructure of GTD-111 superalloy laser weld joints. For this purpose, a Nd:YAG pulsed-laser with a maximum power of 400 w was used. Numerical computation results through the Rosenthal equation showed that the length of the various welding regions including HAZ, PMZ and MZ increased with increasing pre-welding sample from − 25 to 200 °C, which was in agreement with the experimental results of the experiments. By reducing the sample temperature before to welding from 200 to − 25 °C, the heating rate increased from 162,857 to 195,000 °C/s. The high heating rate in pre-cold conditions increased the cooling rate of the weld metal and thereby decreased the segregation of the alloying elements. In the cast condition, the $$\gamma^{\prime }$$ , $$\gamma\text{-} \gamma^{\prime }$$ eutectic, Cr–Mo boride and Ni–Zr intermetallic phases were responsible of liquation cracks in HAZ, which were all dissolved in austenitic matrix by heat treatment at 1230 °C. The results of HAZ microstructural studies showed that by increasing the liquid film Thickness (LFT) due to the liquation of $$\gamma^{\prime }$$ and MC phases, the susceptibility to liquation crack was reduced due to increased stress-relief. However, as the LFT increases due to the liquation of the $$\gamma\text{-} \gamma^{\prime }$$ , Cr–Mo phases, the susceptibility to crack liquation increases due to the decrease in stress-relief for crack formation. This is attributed to the high $$\Delta T$$ of the $$\gamma\text{-} \gamma^{\prime }$$ , Cr–Mo phases and the low $$\Delta T$$ of the $$\gamma^{\prime }$$ and MC phases.