LASER METAL DEPOSITION ON PWA 1483 SINGLE CRYSTAL SUPERALLOY

摘要

Laser Metal Depositions (LMDs) of Rene41 and IN738 on single crystal (SX) PWA1483 Superalloy have been investigated using a fiber-coupled high power diode laser system. To determine the parameters, the effects of laser power, scanning velocity and powder feed rate on single track profile were studied. Multi-layer depositions were carried out using different parameter combinations. The results showed that deposition process and track profile could be precisely controlled during LMD. Microstructure of deposited multi-layers using IN 738 powder consisted of primary γ dendrite and MC type carbides containing high contents of Ti and Ta. The orientation of γ dendrites was strongly affected by processing condition. Most of cracks were observed at large-angle grain boundaries. Deposition of IN 738 powder demonstrated much higher susceptibility to cracking than using Rene 41 powder. Almost crack-free volume has been produced with IN 738 by controlling deposition condition to achieve epitaxial columnar-dendritic growth from substrate and from the previous layer. No cracks could be found in Rene 41 deposits even at misoriented grain boundaries. The mechanism of cracking was also investigated and discussed. Finally, LMD using Rene 41 powder has been successfully applied to repair cracked platform of a cracked SX PWA 1483 turbine blade.