摘要
Abstract
This paper presents a failure analysis of the abnormal vibration fracture of Ta1 hollow cathode tantalum tube brazing joints through various methods,including macroscopic examination,metallographic examination,micro-hardness testing,confocal surface topography detection,and fracture and energy spectrum analysis.The study investigated the effects of temperature and atmosphere during the thermal processing of Ta1 hollow cathode tantalum tubes and gold-nickel brazing joints.With the fracture morphology undergoing multiple changes,the fracture of the cathode tantalum tube expanded from the outer brazing joint towards the inner wall of the tube.By integrating the history of the part's test,it was inferred that after the initial vibration test,a fatigue crack had already penetrated through the brazing joint and expanded approximately 4 μm into the tantalum tube.A melting layer approximately 57 μm deep was observed within this fracture area.After impact tests,the brittle crack within the tantalum tube expanded inward by about 100 μm,exhibiting a brittle fracture morphology.During the second round of vibration testing,the fatigue crack,originating from the previous tests,continued to expand,reducing the remaining effective cross-section of the tantalum tube,ultimately leading to instantaneous fracture under the influence of vibration load.Based on the experimental analysis,the NiTa2 melting erosion layer at the crack source was formed due to overheating during the sintering nickel process,which reduced the effective thickness and strength of the tantalum tube.After sintering a nickel layer,partial grain growth was observed in the tantalum tubes.High temperature and a hydrogen atmosphere could transform the ductile fracture of the industrial pure tantalum at room temperature into a brittle fracture.Based on the analysis,it is recommended to control the sintering temperature of nickel and the subsequent induction brazing temperature,time and distance to avoid the formation of NiTa 2 melting layer on the tantalum tube and to mitigate the risk of embrittlement due to high temperature and hydrogen environment.关键词
空心阴极/工业纯钽/金镍钎焊/振动断裂/熔蚀/氢气致脆Key words
hollow cathode/industrial pure tantalum/gold-nickel brazing/vibration fracture/melting erosion/hydrogen embrittlement分类
矿业与冶金
