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传统牌号高强镍基高温合金具有较宽的凝固温度区间、较高比例的低熔点共晶相,在增材制造快速非平衡凝固过程中易产生裂纹等缺陷;同时,热处理过程中残余应力释放和γ’相快速析出导致应变时效裂纹的形成,严重限制了其在激光增材制造领域的应用与推广。基于此,本文综述了近年来国内外研究组及作者团队在选区激光熔化高强镍基高温合金裂纹形成机理与抗裂纹设计(成形工艺参数优化、热处理制度调控以及合金成分设计)领域相关的研究进展,并对激光增材制造γ’相强化镍基高温合金裂纹调控的研究进行了展望。 相似文献
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铸造镍基高温合金广泛用于燃气轮机与航空发动机叶片等高温部件,长时间运行过程中经常发生叶片局部损伤失效,其维修或更换成本极高。通过增材修复来恢复局部损伤叶片的性能,将极大地降低制造成本、缩短制造周期、节约资源,具有极大的社会效益和市场价值。本文针对燃气轮机与航空发动机用铸造镍基高温合金部件的服役工况与失效形式,结合铸造镍基高温合金的成分、组织与性能特点,系统分析了增材修复时出现裂纹的类型、特点及形成机理,阐述了各类裂纹的主要影响因素,从增材工艺和材料两方面分类综述了减少或避免裂纹的增材修复工艺与技术现状,分析了不同增材修复方法的优缺点与未来可能的研究热点。 相似文献
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Al、Ti是镍基高温合金主要沉淀强化元素,随着Al、Ti含量的增加,镍基高温合金γ'-Ni3(Al,Ti)相体积百分数增加,高温强度增加,但是热裂纹敏感性也随之增加,如何利用熔焊工艺实现高Al、Ti镍基高温合金材料的表面无损伤熔焊处理一直是高Al、Ti镍基高温合金叶片与热端部件制造与再制造面临的难题.文中从高温合金表面熔焊修复与强化问题出发,着重介绍了高温合金焊接冶金问题及焊接性改善途径、激光与微弧火花两种低热输入熔焊工艺在高温合金表面修复与强化领域的研究与应用进展.分析表明:高Al、Ti镍基高温合金表面熔焊处理的主要难题是其高的热裂纹敏感性,主要表现在焊接或焊后热处理过程中容易产生凝固裂纹、液化裂纹、应变时效裂纹,采用惰性气体保护、改变基体组织状态、使用低强度的合金焊料、降低热输入等措施可有效改善其焊接性;激光、微弧火花等低热输入焊接工艺在解决高Al、Ti镍基高温合金表面熔焊问题方面具有极大的潜力. 相似文献
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电弧增材制造技术基于分散累加原理,可实现镍基高温合金复杂结构快速无模加工,是一种广受关注的先进加工技术。该研究以高温耐蚀合金Inconel 617增材制造块体为研究对象,采用OM,SEM及万能拉伸试验机等手段分析了增材制造镍基合金块体微观组织及力学性能。研究结果表明,Mo元素在柱状枝晶间偏析,促使大尺寸的Laves相沿枝晶析出。在拉伸应力下,Laves相由于脆性较高,易发生断裂,诱发裂纹萌生。由于裂纹扩展路径在不同方向拉伸时存在显著差异,导致增材制造构件沿沉积方向强度(900 MPa)显著高于垂直沉积方向强度(700 MPa)。该研究为电弧增材制造镍基合金的组织性能调控奠定了一定基础,为进一步推动电弧增材制造镍基合金构件的应用进行了有益探索。 相似文献
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采用激光增材技术修复了损坏的K465镍基高温合金航空发动机涡轮叶片,研究了激光增材修复K465高温合金的裂纹特征,分析了开裂机理,并采取有效措施实现了裂纹控制。结果表明:激光增材修复K465合金的裂纹产生于热影响区,并沿晶界扩展到修复区中,为液化裂纹;热影响区晶界上的连续液膜来源于晶界上大尺寸γ′相的液化,且晶界液化过程中有γ-γ′共晶出现;利用Ansys软件进行应力场模拟的结果显示,基材及熔池之间存在较大热应力;通过同步预热基材,并采用优化的激光工艺参数,实现了K465高温合金单道多层结构的无裂纹激光增材修复。 相似文献
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氢致开裂和应力腐蚀机理的前沿问题 总被引:6,自引:0,他引:6
褚武扬 《腐蚀科学与防护技术》1993,5(3):151-157
本文对各种氢致开裂和应力腐蚀机理进行了评述。指出,把氢促进局部塑性变形和弱键理论以及氢压理论联合起来就有可能发展新的氢致开裂机理;必须深入研究阳极溶解对位错发射,增殖和运动的影响才能提出合理的阳极溶解型应力腐蚀的机理。 相似文献
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环境断裂机理及控制措施 总被引:2,自引:0,他引:2
依据作者所在集体的研究结果,对材料环境断裂这种事故,仿医学,先简述“机理”,然后从事例介绍“控制措施”,这类似于“病理”及“医治案例”。 相似文献
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本文采用悬臂弯曲预裂纹试样应力腐蚀试验方法和紧凑拉伸试样恒载荷法测定了50Mn18Cr40WN奥氏体钢在含C1-和NO3-的水溶液中应力腐蚀以及电解充氢条件下氢致开裂的门槛值,并对应力腐蚀和氢致开裂的裂纹走向与断口形貌进行了观察.50Mn18Cr4WN钢在含C1-和NO3-的水溶液中均能产生应力腐蚀开裂,且在含NO3-的水溶液中比在含C1-的水溶液中应力腐蚀敏感性大.在电解充氢条件下,50Mn18Cr4WN钢也能产生氢致开裂. 相似文献
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《Science & Technology of Welding & Joining》2013,18(1):49-54
AbstractWelding induces residual stresses in structures and may cause buckling distortion if the stresses exceed the critical buckling stress of the structure. Reducing the welding heat input or increasing the structural stiffness reduces or eliminates buckling distortion. However, where, because of the design constraints, structure geometry and weld size are fixed, the transient thermal tensioning process is effective in reducing buckling distortion. An experimental verification and demonstration of transient thermal tensioning for minimising welding induced buckling distortion is presented. Conventional welding was carried out to demonstrate buckling distortion and establish a baseline case. Buckling distortion was eliminated using transient thermal tensioning during welding under the same welding conditions. After buckling distortion was eliminated, angular distortion became evident, which was eliminated using mechanical restraints alongside transient thermal tensioning. Residual stress measurements were obtained using the blind hole drilling method and a comparison of residual stresses for the baseline panel and for the panel with transient thermal tensioning is presented. 相似文献
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J.X. Guo 《Corrosion Science》2003,45(4):735-745
Stress corrosion cracking (SCC) in NaCl solution and hydrogen-induced cracking (HIC) during dynamic charging of Fe74.5Ni10Si3.5B9C2 amorphous alloy were investigated through sustained load tests. The normalized threshold stress of SCC was σSCC/σF=0.04, where σF is fracture strength in air. Anodic polarization and addition of As2O3 into the solution did not change σSCC/σF, but cathodic polarization increased σSCC/σF from 0.04 to 0.31. Cathodic polarization increased but anodic polarization decreased the time to failure during SCC at the constant load of σ=0.27σF.The normalized threshold stress of HIC, σHIC/σF, was linearly decreased with the increase in logarithm of hydrogen concentration (C0) and kept a minimum constant when C0 was larger than a critical value, i.e., σHIC/σF=1.58−0.36lnC0 (C0?74.4 wppm) and 0.1 (C0?74.4 wppm). The threshold stress of HIC during dynamic charging with the maximum current was larger than that of SCC at open-circuit potential. Fracture surfaces of HIC were also different with that of SCC. Experiments indicated that SCC of the amorphous alloy in the NaCl solution is controlled by anodic dissolution process instead of hydrogen. 相似文献
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综述了本研究组近年就应力状态及动态加载过程对氢致开裂的影响所作的一些研究。包括(1)Ⅰ型、(Ⅰ+Ⅱ)及(Ⅰ+Ⅲ)复合型加载条件下的氢致开裂研究;(2)复合型加载条件下裂纹顶端附近氢浓度的再分布;(3)不同加载条件下氢致裂纹形成位置及其与氢致开裂抗力的关系。 相似文献
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Hot cracking susceptibility of the Fe–Ni-based precipitation hardening cast superalloy Alloy 718 was studied by Varestraint weldability testing. The effect of two hot isostatic pressing (HIP) treatments commonly employed in the aerospace industry was investigated in reference to the as cast condition. It was found that the heat affected zone (HAZ) liquation cracking susceptibility increased for samples with pre-weld HIP treatments. The as cast condition disclosed the best response for liquation cracking followed by HIP-1120 (1120°C/4h (HIP)?+?1050°C/1h and furnace cooling to 650°C/1h in vacuum?+?950°C/1h) and HIP-1190 (1190°C/4h (HIP)?+?870°C/10h and furnace cooling to 650°C/1h in vacuum?+?950°C/1h). The amount of the secondary precipitates and base metal grain size was found to be important parameters influencing the cracking susceptibility. Regarding solidification cracking susceptibility, the three conditions appear to behave similarly. 相似文献
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Matthew T. RushPaul A. Colegrove Zhu ZhangDavid Broad 《Journal of Materials Processing Technology》2012,212(1):188-197
An extensive experimental study on a nickel-based superalloy, Rene 80 using autogenous laser welding has been undertaken to determine the effect of the process parameters and weld bead geometry on cracking in the as-welded and post-weld heat treated conditions. Little cracking was observed in the as-welded condition with low powers and beam diameters around 2.5 mm. Welding speed had little effect on the incidence of cracking in the as-welded condition. Investigation of the aspect ratio (penetration divided by width) indicated that little cracking occurred in the as-welded condition when the aspect ratio was approximately 0.5. The same effect was observed with the post-weld heat treated samples. An analysis of the microstructures indicated that the cracking was caused primarily by liquation in the as-welded condition and was exacerbated by post-weld heat treatment cracking during the subsequent heat treatment. Finally the study resolved some of the contradictory findings in the literature on the effect of process parameters on the incidence of cracking in the as-welded and post-weld heat treated conditions. 相似文献