复杂空心涡轮工作叶片表面细晶工艺研究

Surface Grain Refinement Process for Hollow Turbine Blade with Complicated Shape

针对由K465合金制造的复杂、空心涡轮工作叶片表面细晶的不同要求,研究了制备叶片陶瓷型壳时,采用在精铸型壳内表面均匀涂挂一层350号铝酸钴作为表面细晶孕育剂,其加入量分别为0、35%、45%～65%及100%时对叶片表面低倍晶粒度的影响;同时研究了细晶孕育剂加入量一定时,浇注叶片时冷却环境对叶片表面低倍晶粒度的影响。研究结果表明,未经孕育处理的试片表面晶粒粗大,而经铝酸钴细晶孕育剂处理后试片表面晶粒细小。当铝酸钴加入量为45%～65%时,叶片采用热型浇注,型壳细砂做填砂,能够使复杂、空心涡轮工作叶片表面低倍晶粒度的合格率达到90%以上。另外,工艺可行性验证结果也表明,中、外叶片显微组织、力学性能相当。

The aim of the present research is to provide a method for producing fine surface grains for hollow turbine blade with complicated shape. By fabricating ceramic shell mold for hollow turbine blade with complicated shape and coating uniformly the internal surfaces of shell mould with cobalt aluminate coatings, the influence of cobalt aluminate as inoculant on the grain sizes of turbine blade surface was mainly studied when the addition amount of cobalt aluminate was 0, 35%, 45%-65% and 100%, respectively. At the same time, the effects of cooling circumstances of the blades on external grain sizes were also experimented when keeping the addition amounts of cobalt aluminate unchanged. The results show that coarse external grains were obtained for sample without coating the internal surfaces of shell mould using cobalt aluminate coatings; while for sample with cobalt aluminate coatings on the internal surfaces of shel~ mould, fine external grains were obtained. When the addition amount of cobalt aluminate is between 45%-65% and blades were poured using heated shell mould and fine sand as backing sand, the qualification rate for grain size of hollow turbine blade surface up to the prescribed requirements is over 90%. In addition, comparison was conduced between home-made and foreign-made blades. The results indicate that their microstructures and mechanical properties have little difference.