压力对镍基单晶液相扩散焊接头组织及性能的影响

发布时间：2018-02-12 21:52

本文关键词： 镍基单晶高温合金 TLP 压力母材液化组织性能　出处：《南昌航空大学》2016年硕士论文　论文类型：学位论文

【摘要】：镍基单晶高温合金具有优良的高温力学性能,是航空发动机涡轮叶片的主要材料。随着飞机涡轮叶片冷却形式的发展,空心型腔越来越复杂,单凭铸造技术很难实现结构复杂叶片的制造,采用两半对开或组合式空心叶片是解决脱芯难题的先进方案,其制备过程必然涉及到材料的连接问题。本文采用厚度为20μm的非晶箔状BNi9作为中间层,对厚度为10mm的DD407镍基单晶进行TLP连接。研究无压和压力作用下工艺参数对镍基单晶TLP连接接头组织及性能的影响,通过金相组织观察和能谱测试,详细分析了无压和压力作用下接头形貌及各元素分布。并对压力作用下,焊缝中心和焊缝边缘接头形貌及焊接温度和保温时间对接头组织性能的影响进行了分析。通过对比不同压力作用下,接头组织性能及元素扩散,进一步探索了压力在TLP中作用机制。研究结果表明:无压作用下,接头抗拉强度随着焊接温度升高先增大后减小,随着保温时间延长先增大后趋于平缓,当焊接温度为1150℃,保温时间为2h时,接头强度最大为954.1MPa,断裂发生在母材中,断口存在白色的撕裂带,分析为准解理断裂;接头组织随着焊接温度和保温时间增大,越来越均匀,当焊接温度为1150℃,保温时间4h后,焊缝中心组织完全均匀化,接头中心元素分布均匀。有压作用下,接头抗拉强度随着压力的增加而增加,当压力为3MPa时,接头强度最大为744MPa,断裂发生在母材,相对于无压下,断口未见白色的撕裂带,表现为瞬间拉断,并且压力的作用使得母材中强化相γ′发生严重变形。3MPa作用下,焊缝中心组织均匀,主要为γ、γ′;焊缝边缘存在残余共晶区,组织分别为深灰色CrB,浅灰色Ni3B-γ共晶相,基体γ、γ′相;扩散区中近缝颗粒状组织为(Cr,Mo,W)3B2,远离焊缝针状组织为(Cr,Mo,W)5B3。3MPa作用下,接头抗拉强度随着焊接温度的增加变化不大,最大抗拉强度能达到776MPa,随着保温时间的增加先增大后减少,最后趋于平缓,当保温时间为2h时,接头抗拉强度为744MPa。断裂均发生在母材。压力的作用机制,起始阶段,在压力的作用下,母材表面和中间层之间凸起的部位被压平。随着温度的升高,中间层首先达到熔点并迅速熔化,降熔元素B往母材扩散,当扩散量达到一定值时,母材开始液化。压力的施加,使得焊缝中心液相被挤压到焊缝边缘,从而使得焊缝中心未发生等温凝固,原子间进行液相扩散,使得组织均匀。而焊缝边缘各元素浓度增大,降熔元素浓度增大对焊缝边缘的母材继续产生液化,使得焊缝边缘的宽度更大。焊缝边缘残留的液相在冷却过程中产生共晶。
[Abstract]:Nickel base single crystal superalloy has excellent high-temperature mechanical properties, is the main material of aeroengine turbine blade. With the development of aircraft turbine blade cooling form, the hollow cavity is more and more complex, with casting technology is difficult to achieve the complex structure of blade manufacturing, the two half of open or combined hollow blade is advanced to solve scheme the core problem, its preparation process involves the connection material. This paper uses the thickness of amorphous foil BNi9 20 m as the middle layer with a thickness of DD407 nickel base single crystal 10mm TLP. Study on influence of process parameters on pressure and pressure of nickel base single crystal TLP connection and the performance of joint organization, through the microstructure observation and energy spectrum test, a detailed analysis of the distribution and morphology of joint elements without pressure and pressure. And the pressure, the center of weld and weld seam edge joint. And the welding temperature and holding time on the microstructure and properties of welded joint are analyzed. Through the contrast effect under different pressure, microstructure and mechanical properties of joint element diffusion, to further explore the mechanism of pressure in TLP. The results show that: no pressure, tensile strength of joint with the welding temperature increased first and then decreased with thermal insulation time first increased and then leveled off, when the welding temperature is 1150 DEG C, the holding time is 2h, the joint strength is 954.1MPa, the fracture occurred in the parent metal, there is white with tear fracture analysis to quasi cleavage fracture; microstructure with welding temperature and holding time increasing, more and more uniform, when the welding temperature 1150 C, the holding time after 4h, the weld center organization completely uniform, joint center elements evenly distributed. The pressure under the action of tensile strength increases with increasing pressure, when the pressure is 3M Pa, the joint strength is 744MPa, the fracture occurred at the base metal, with no pressure, no fracture white tear tape, is instantly pulled off, the pressure and the parent material strengthening phase in gamma 'serious deformation under the action of.3MPa, the center of weld microstructure, mainly for gamma, gamma'; the presence of residual eutectic zone of the weld edge, the microstructures are dark grey CrB, light grey Ni3B- gamma eutectic phase, the matrix gamma, gamma prime phase; diffusion region near the joint organization for granular (Cr, Mo, 3B2, W) from acicular tissue (Cr, Mo, W) 5B3.3MPa under the action of joint the tensile strength of welding with the increase of temperature changes little, the maximum tensile strength can reach 776MPa, with the increase of the holding time increases first and then decreases, finally tends to be stable when the holding time is 2h, the tensile strength of 744MPa. fracture occurred in the base metal. The mechanism, the pressure in the initial stage, the effect of pressure Under bump between base material surface and middle layer parts are flattened. With the increase of temperature, the middle layer and the first to reach the melting point rapidly melting, melting pointdepressants B diffusion into the parent material, when the diffusion amount reaches a certain value, the parent material to liquefaction. Pressure, the liquid is extruded to the weld center the edge of the weld, so that the weld center without the occurrence of isothermal solidification, liquid phase diffusion between atoms, the uniform microstructure and weld edge. Each element concentration increases, the increase of the concentration of the parent metal melting pointdepressants on the edge of the weld continues to produce liquefaction, make the weld edge width is greater. The edge of the weld residual liquid generated in eutectic during the cooling process.

【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG453.9

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