空气起动机K424合金动力涡轮叶轮轮毂的微裂纹研究

Study on Microcracks of K424 Alloy Power Turbine Impeller Hub of Air Starter

将K424镍基等轴晶高温合金整体动力涡轮叶轮在大功率起动1 000次后故障件与定型件、样机件对比,对叶片与轮毂转接处微裂纹及断口形貌、化学成分、力学性能、金相组织等的变化规律以及形成机理进行了研究。结果表明,故障件的微裂纹属于交变应力作用下的低周疲劳断裂,裂纹源位于轮毂表面附近,沿着碳化物边界扩展;晶界强化元素B,Zr偏低,组织形貌存在一定量骨架状碳化物相等缺陷,这些因素导致了K424涡轮叶轮叶片与轮毂转接处微裂纹的形成。

The fault parts of K424 nickel base equiaxed superalloy whole power turbine impeller were compared with the finalizing parts and prototype parts after the high power starting 1000 times, the changes of microcracks and fracture morphology, chemical composition, mechanical properties, metallographic structure and the formation mechanism of the blade and hub were studied. The results show that the microcrack of the fault part belongs to the low cycle fatigue fracture under the action of alternating stress, and the crack source is near the surface of the wheel hub and extends along the carbide boundary. The grain boundary strengthening element B, Zr is low, and there is a certain amount of matrix carbide equivalent defects in the structure appearance, these factors lead to the formation of microcracks in the rotor blades of the K424 turbine impeller and the hub.