Influence of heat treatments and chemical composition on SCC susceptibility during repairing procedure of overlaying of Inconel 182 by laser surface melting

Abstract

A practical repairing technique using laser surface melting (LSM) was developed to remove the stress corrosion cracking (SCC) in overlaying of Inconel 182. Influence of microstructure of different heat treatments performed during repairing process on intergranular cracking/intergranular stress corrosion cracking (IGC/IGSCC) susceptibility was discussed. The intergranular precipitate was identified as M23 C6 by TEM. The microstructure with no intergranular precipitate and refiner sub-grain after LSM process shows excellent IGC/IGSCC resistance. The stress relief heat treatment induced severe microstructure of high IGC/IGSCC susceptibility, owing to the semicontinuous intergranular precipitation. The influence of Nb/C ratio on IGC/IGSCC susceptibility of three nickel based superalloys after LSM process was also investigated. For both of the Inconel 182 alloys with different Nb content, the microstructure after LSM process and following sensitisation treatment showed precipitation free grain boundary. The results of corrosion tests also indicated that the material with higher Nb/C ratio showed higher IGC/IGSCC resistance after LSM process and following sensitisation treatment.

Precipitation and Cr depletion profiles of Inconel 182 during heat treatments and laser surface melting

“…Tsai et al (2005) studied the IGC occurrence of Inconel 182 by employing chemical and electrochemical evaluation techniques. Recently, in our previous study (Bao et al, 2005a(Bao et al, ,b, 2006a, laser surface melting (LSM) has been considered as one of the useful surface modification techniques to repair and improve corrosion resistance of overlaying of Inconel 182 in parts of nuclear plants.…”

Comparisons of 30Cr2Ni4MoV rotor steel with different treatments on corrosion resistance in high temperature water

“…It have been generally accepted that LSM can be used for improving the corrosion resistance of metallic alloys through the homogenization/refinement of microstructure, dissolution/redistribution of precipitates or inclusions and phase transformation [7]. LSM was also used to improve the SCC resistance of metallic alloys [8][9][10][11].…”