航空发动机用铝合金加力泵涡壳的失效分析

Failure analysis of aluminum alloy scroll-case on intensifier pump used in aero-engine

对一种航空发动机供油系统铝合金涡壳的气蚀特点和失效机制进行了分析。结果表明,气蚀区的分布与油流流向间有明显的相关性,气蚀损伤主要发生在有涡流形成及压强变化的区域;微观气蚀表面由大量尺寸在40-60μm的气蚀凹坑相互叠加组成,单个气蚀凹坑内壁光滑,边缘呈波浪状泼溅;气蚀区表面有疲劳裂纹和冲蚀形貌;冲蚀常伴随气蚀同时发生,最终的损伤是“气蚀＋冲蚀”复合作用的结果;气蚀的发生有明显的相选择行为,较软的α-Al相通常较Si相优先被气蚀,使材料表面强度下降,从而导致材料破坏的加剧;抑制相选择行为能够改善涡壳的抗气蚀性能。

The failure mechanism and cavitation erosion characteristics of an aluminum alloy scroll-ease used in aero-engine fuel system were investigated. The results show that there is an obvious correlation between the distribution of cavitation erosion zone and the direction of oil flow. Cavitation erosion mainly occurs in the zone where there are vortexes and variety of intensity pressure. The eroded surface is composed of many erosion pits which are laid to overlap each other. The sizes of these erosion pits are in the range of 40 - 60 μm. The inner wall of each erosion pit is even, and the margin shows splash morphology. Cracks and outwash morphologies can be observed on the eroded surface. The erosion corrosion usually occurs with cavitation erosion. So, the failure of the intensifier pump scroll-case in fuel system is caused by the complex mechanism of cavitation erosion and erosion corrosion. There are ＂phase select＂ behaviors in cavitation erosion. The α-Al phase which is softer than Si phase is eroded preferentially. This causes the surface strength decrease and the damage to be aggravated. The cavitation erosion resistance can be improved by suppressing the ＂phase select＂ behaviors.