MICROSTRUCTURAL AND MECHANICAL ASPECTS OF FRICTION WELDED DISSIMILAR JOINTS FOR AERO ENGINE APPLICATION

Abstract

Gas turbine engines demand material with unique properties like high-temperature oxidation and corrosion resistance, high specific strength, etc. All over the world material development to meet these requirements has led to the development of novel alloys. While Titanium base alloys are used in the low-temperature regime of the gas turbine engine, Nickel-basedsuperalloys are used for hot end components of the engine. With the increase in the temperature requirement for the turbine parts, the form of the Ni-based superalloys changed from wrought to cast superalloys. As an inherent process of investment cast superalloy blades and vanes which has serpentine passages for air cooling, these passages are required to be closed after casting. The numerous adapters also need to be joined on the cast superalloy casings for various instrumentation, lube oil ports. These cast superalloys are nonweldable and joining these pose a challenge. In this present investigation, the joining of the Nibasedsuperalloy BZL12Y and martensitic stainless steel AE961W using rotary friction welding process. The mechanical properties of the dissimilar joints were evaluated as per the ASTM standards. Microstructural features of various regions of welded joints using optical microscopy (OM) and scanning electron microscopy (SEM). The material is welded in different condition to obtain the maximum tensile strength of the weld joint. From this investigation, it was found that the combination of aging and h & t condition weld joint gives good strength and a stable hardness value. Correlation between tensile properties and microstructural features were analyzed and reported in this paper.