Session: 18-02 Service of Gas Turbine Components - Life Assessment & Repair Processes

Paper Number: 80473

80473 - Advanced Tip Repair of Single Crystal HPT Blades With LW3 and LW4280 Welding Materials 

The high pressure turbine (HPT) blades manufactured from single crystal (SX) materials exhibit tip degradation resulting primarily from abrasion, thermal fatigue cracking (TMF), creep, and oxidation.  Currently, Gas Tungsten Arc Welding (GTAW) and Laser Beam Welding (LBW) with Merl 72 (M72) and Rene 142 (R142) welding materials are used for repairing the tips of SX HPT blades. Tips repaired with M72, despite superior oxidation resistance of the cobalt welding material, are prone to cracking due to the low mechanical properties of the M72 welds at temperatures exceeding 1800°F. Additionally, despite the high strength of R142 in its cast condition, R142 welds are prone to weld stress-strain cracking and thus requires preheating of a blades above 1700°F (926°C). Preheating can adversely affect the inert atmospheric conditions of the argon protection. This inadequate shielding of the welding area may result in contamination of welds with non-metallic inclusions which reduce creep and TMF properties. 

 

The current study focuses on the substantiation of replacing M72 with alternative LW3 and LW4280 nickel based welding materials for minor dimensional restoration and full tip replacement for SX HPT blades with a solid tip cap. LW3 and LW4280 after post weld aging heat treatment comprise 28 vol.% and 49 vol.% gamma prime phase respectively. A time-transient thermal mechanical Finite Element Analysis (FEA) of the SX HPT blade was completed for takeoff, cruise, and landing conditions. The resultant temperature and stresses from the FEA study were used as the basis for the testing of dissimilar and similar weld joints as well as the qualification for the tip repair of HPT blades. Tensile and stress rupture properties of dissimilar SX-LW3 and SX-LW4280 welds produced at ambient temperature using manual GTAW and Laser Direct Energy Deposition (L-DED) on a LAWS1000 welding system utilizing a 3D additive manufacturing (AM) concept were studied. It was demonstrated that LW4280 welds had superior stress rupture, and fatigue properties when compared to M 72. Cyclic oxidation resistance of LW4280 at 2048°F was found to be sufficient to ensure required durability of repaired blades for 6,000 cycles in cases of damaging of protective coatings. Some examples of repairs of HPT blades using these developed materials and technologies are provided. 

Presenting Author: Anthony Chan Liburdi Turbine Services

Presenting Author Biography: Anthony Chan is a Senior Engineer at Liburdi Turbine Services. He graduated from McMaster University with a Bachelor’s degree in Mechanical Engineering and Management as well as a Master’s in Business Administration. He has 11 years of experience in the repair of gas turbine components. Anthony has led and contributed to various repair developments for hot section components of flight, aero derivative and industrial gas turbines.

Authors:

Anthony Chan Liburdi Turbine Services
Alexandre Gontcharov Liburdi Turbine Services
Paul Lowden Liburdi Turbine Services
Thomas Mikolajewski Liburdi Turbine Services
J J Sixsmith Liburdi Automation
Robert Tollett Liburdi Turbine Services
Clayton Greer Delta Air Lines