OVERVIEW ON THE DEVELOPMENT OF LIBURDI TURBINE SERVICES WELDABLE Ni-BASED SUPERALLOYS AND TECHNOLOGIES FOR REPAIR AND 3D AM OF TURBINE ENGINE COMPONENTS

High gamma prime Ni-based superalloys comprising 3.5 % Al or greater are difficult to weld due to high propensity of these materials to weld solidification, heat affected zone liquation, and stress-strain cracking. In this study the root cause analysis of cracking and overview on the developed weldable Ni- based superalloys for repair of turbine engine components manufactured from equiaxed, directionally solidified, and single crystal material as well as for 3D AM is provided. It is shown that the problem with the solidification and HAZ liquation cracking of turbine engine components manufactured from EX and DS superalloys was successfully resolved by modification of welding materials with boron and silicon that formed on cooling of a homogeneous welding pool composite-like structure comprising the interconnected framework of high temperature dendrites and sufficient amount of interdendritic eutectic matrix enabling self-healing of liquation cracks along the weld - base material interface. Transformation of continues intergranular B-based eutectics into refractory discrete Re, Mo, W, and Nb borides during post weld heat treatment enabled formation of ductile welds with strength up to 71 KSI at 1800°F. Mechanical properties and structure of welds as well as application of LW7 and LW3 welding wires and LW42B and LW47B powder blends for repair of turbine engine components by gas tungsten arc welding and laser beam welding respectively is provided. For crack repair of turbine engine components and 3D ductile LW4280, LW4280W and LW4280LCT materials were developed. It is shown that LW4280W and LW4280LCT welding materials comprising 30 - 32 wt.% Co produced sound welds by GTAW-MA on various SC and Rene 80 DS materials. Welds demonstrated high ductility, desirable combination of strength and oxidation properties for tip repair of turbine blades. Examples of tip repair of turbine blades are provided.