燃气轮机涡轮叶片在高温、腐蚀以及复杂应力环境下,叶顶容易磨损甚至断裂,通常采用修复的方式降低叶片维护成本,但传统焊接修复具有热影响区大、焊后组织退化的问题,降低了修复叶片的服役寿命.采用激光粉末床熔融(Laser Powder Bed Fusion,L-PBF)修复CM247LC柱状晶叶片,具有热影响区小、可实现柱状晶组织接续的优势.采用不同晶体取向的柱状晶基板模拟受损柱状晶叶片,研究基板晶粒形貌(柱状晶与等轴晶)和取向(基板<001>取向//成形方向(Building Direction,BD)、<111>//BD、<110>//BD)对修复区晶粒外延生长的影响规律.结果表明,采用<001>//BD柱状晶基板与等轴晶基板的修复区中<001>取向晶粒的含量分别为94.2％和11.1％,柱状晶基板较等轴晶基板更利于柱状晶的外延生长;不同晶粒取向的基板对修复区<001>织构含量影响显著,修复区<001>织构含量从高到低依次为:<001>//BD柱状晶基板,为94.2％;<111>//BD柱状晶基板,为34.0％;<110>//BD柱状晶基板,为24.4％.
Study on the Epitaxial Growth Behavior of Columnar Crystal Blades of CM247LC in Laser Additive Manufacturing Repair
The tips of turbine blades in gas turbines are prone to wear and even fracture under high temperature,corrosion,and complex stress environments.Repairing the blades is a common method to reduce maintenance costs.However,traditional welding repairs often resulted in a large heat-affected zone and suffer from microstructural degradation,which reduces the service life of the repaired blades.This study utilized Laser Powder Bed Fusion(L-PBF)to repair CM247LC columnar crystal blades,offering advantages such as a smaller heat-affected zone and the capability to achieve continuity in columnar crystal structures.Different crystal orientations of columnar crystal substrates were used to simulate damaged columnar crystal blades.The research investigated how the grain morphology(columnar versus equiaxed grains)and orientation(substrate<001>orientation//building direction(BD),<111>//BD,<110>//BD)affected the epitaxial growth of grains in the repair zone.The results indicate that the content of<001>oriented grains in the repair zones using<001>//BD columnar crystal substrates and equiaxed grain substrates are 94.2％and 11.1％,respectively,demonstrating that columnar crystal substrates are more favorable for the epitaxial growth of columnar crystals compared to equiaxed substrates.Furthermore,the influence of different substrate grain orientations on the<001>texture content in the repair zone is significant,with the<001>texture content ranking from highest to lowest as follows:94.2％for the<001>//BD columnar crystal substrate,34.0％for the<111>//BD columnar crystal substrate,and 24.4％for the<110>//BD columnar crystal substrate.
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