Preparation and property of seal coating for gas turbine compressor

Double-layer structure of seal coating which consisted of a Ni5Al bond coating and a Ni25 graphite top coating were prepared on steel substrate of gas turbine compressor cylinder block.Bond coating was prepared by atmospheric plasma spraying and top coating was prepared by flame spraying.The microstructure,mechanical properties and abradability of the coating were characterized by scanning elec-tron microscope(SEM),hardness tester,universal testing machine,thermal shock testing machine and abradability testing machine.The res-ults show that the overall spraying structure of the seal coating is uniform,the nickel metal phase is the skeleton supporting the entire coat-ing,and the coating is well bonded without separation.The seal coating has a bonding strength of not less than 7.7 MPa,excellent thermal stability,and thermal shock resistance cycle numbers at 500℃more than 50;the scratch length,deepest invasion depth and wear amount of the coating increase with rise of test temperature,with almost no coating adhesion,indicating that the seal coating has excellent abradability.

35CrMoA螺栓失效分析和改进措施

汽轮机运行时,转子上连接联轴器的高强度螺栓如果发生断裂,轻则需要停机维修,重则造成较大事故。为了找出某汽轮机35CrMoA钢制螺栓断裂失效的原因,对失效件的宏观断口形貌进行了观察,并采用光学显微镜、扫描电镜、X射线能谱仪、硬度计设备等对失效件的微观断口形貌、显微组织、硬度和化学成分等进行了理化试验和分析,结果表明早期淬火裂纹导致了该螺栓发生沿晶脆性断裂。杆部转接处在冷镦变形过程中形成了非正常组织,硬度为430~500 HV,远高于标准硬度,其经过淬火后扩展成淬火裂纹,最终导致螺栓断裂。提出了改进冷镦工艺并增加冷镦后的热处理的建议。研究成果可为冷镦工序后硬度异常问题的处理提供参考。

Al_(62)Cu_(25.5)Fe_(12.5)准晶磨料的制备及性能

由非自耗电弧熔法制备Al62Cu25.5Fe12.5单相准晶合金,再将该合金进行球磨处理制备了Al62Cu25.5Fe12.5二十面体准晶粉末,并以其为磨料配制研磨膏,对软金属Al进行表面研磨处理。结果表明:经准晶研磨处理后的纯Al表面平整无划痕,粗糙度为Ra=0.306,达到一般精研要求。与传统金刚石磨料不同,这种准晶研磨材料在机械研磨时可避免造成对软金属表面的二次划伤,且表现出对软金属基体表面缺陷的修复能力。

大型离心式压缩机成品机壳补焊技术

某大型离心式压缩机机壳有多处焊接缺陷,且机壳已是成品状态。根据壳体材料成分、结构特点、缺陷分布、除应力难等情况,设计了合理的防变形措施、补焊顺序及焊接参数来控制焊接变形,采用振动时效去除焊接残余应力,成功完成壳体补焊。结果表明,焊缝质量符合NB/T 47013—2015标准Ⅱ级的质量要求;振动时效效果明显,大部分焊缝的残余应力降低约30%~40%,部分焊缝更消除了约57%的残余应力;机壳焊后变形较小,壳体水平中分面最大高度差约4~5 mm,中分面各处沿径向外侧最大扩张变形不超过2 mm。文中研究结果为压缩机、汽轮机等大型壳体成品阶段的大面积补焊及变形控制提供了宝贵的经验。

分段式过盈配合零部件拆卸工艺研究

介绍3种节流阀套筒常用的拆卸法,分析各自的优缺点,对类似的分段式过盈配合结构提出设计意见,为广大的机械设计者提供参考。