Study on Micro Cracks of K424 Alloy Power Turbine Impeller Hub of an Air Starter

The fault piece K424 nickel base equiaxed superalloy power turbine impeller has a micro crack after 1000 times of high-power starting. After comparing the fault parts with the stereotype, the fracture surface, the chemical composition, the mechanical properties and the metallographic structure, the changes of the microstructure and mechanical properties of the turbine impeller and the mechanical properties of the turbine impeller are analyzed in five aspects. The results show that the micro crack of the fault part belongs to the low cycle fatigue fracture which occurs under the alternating stress. The crack source is located near the surface of the wheel hub and extends along the carbide boundary, and the grain boundary strengthening element B, Zr is low, and the microstructure exists a certain amount of skeleton carbide phase defects. These factors lead to the K424 turbine. The formation of micro cracks on impeller blades and hub joints. (paper)