等离子喷焊表面质量的金属磁记忆检测

发布时间：2019-02-15 05:45

【摘要】：等离子喷焊技术是一种典型的表面修复技术,凭借其能量集中、效率高、工艺稳定性好、易于实现自动化等优点获得了广泛的应用。喷焊过程中等离子弧中心温度可达15000 K以上,使基材产生较大的热损伤,且熔覆层服役过程中往往承受拉伸疲劳载荷的作用,应力集中、疲劳已成为熔覆层损伤的主要形式之一,对这些损伤进行无损检测已成为再制造构件表面修复的关键环节。金属磁记忆检测是一种新型的无损检测方法,研究基材热损伤、熔覆层应力和疲劳的磁记忆检测,对促进该技术在表面工程的发展具有重要的研究意义及应用价值。本文首先研究等离子喷焊热应力对表面磁记忆信号的影响。制备等离子喷焊熔覆层,检测喷焊前后距熔覆层不同距离检测线上的磁记忆信号,分析磁信号波峰波谷差△Hp(p)随热应力大小的变化,结合热影响区微观组织和X射线衍射峰半高宽的变化,探讨等离子喷焊热应力的磁记忆检测方法。其次制备标准的等离子喷焊熔覆层静载拉伸试样,用TSC-2M-4磁记忆检测仪离线检测不同拉伸应力下熔覆层表面磁信号,分析磁信号法向分量梯度K和切向分量均值Hp(x)avg同拉伸应力之间的量化关系,并进一步基于磁畴变化和磁机械效应,探讨等离子喷焊熔覆层静载拉伸应力的磁记忆技术定量评估方法。最后针对标准的等离子喷焊熔覆层疲劳试样,观察熔覆层在不同循环周次以及断裂前后表面的磁记忆信号、熔覆层塑性变形和微观组织结构的变化规律,分析Hp(y)最大梯度Kmax和Hp(x)峰值Hp(x)avg随循环周次增加的变化关系,提出基于Kmax的熔覆层损伤参数D,探讨等离子喷焊熔覆层拉伸疲劳损伤的磁记忆检测方法。
[Abstract]:Plasma spray welding is a typical surface repair technology, which has been widely used because of its advantages of concentrated energy, high efficiency, good process stability and easy to realize automation. In the process of spray welding, the center temperature of plasma arc can reach more than 15000 K, which makes the substrate produce great thermal damage, and during the service of the cladding layer, it often bears the function of tensile fatigue load, and the stress is concentrated. Fatigue has become one of the main forms of cladding damage. Nondestructive detection of these damage has become a key link in surface repair of remanufactured components. Metal magnetic memory detection is a new nondestructive testing method. It is of great significance and application value to study the thermal damage, cladding stress and fatigue of the substrate, to promote the development of the technology in surface engineering. In this paper, the effect of thermal stress on surface magnetic memory signal in plasma spray welding is studied. The plasma spray welding cladding layer was prepared to detect the magnetic memory signal on the detection line at different distances from the cladding layer before and after spray welding. The variation of the magnetic signal peak and valley difference (Hp (p) with the thermal stress was analyzed. Combined with the change of microstructure and the half-width of X-ray diffraction peak in the heat-affected zone, the magnetic memory measurement method of thermal stress in plasma spray welding is discussed. Secondly, the standard plasma spray welding coating static load tensile specimen was prepared, and the surface magnetic signal of the cladding layer under different tensile stress was detected by TSC-2M-4 magnetic memory detector. The quantization relationship between magnetic signal normal component gradient K and tangential component mean Hp (x) avg and tensile stress is analyzed, and further based on magnetic domain change and magneto-mechanical effect, The magnetic memory technique for quantitative evaluation of static load tensile stress of plasma spray welding cladding is discussed. Finally, the magnetic memory signals, plastic deformation and microstructure of the cladding layer were observed at different cycles and before and after fracture for the standard plasma spray welding cladding fatigue specimen. The relationship between the maximum gradient Kmax of Hp (y) and the peak Hp (x) avg of Hp (x) with the increase of cycle cycles is analyzed. The damage parameter Dof the cladding layer based on Kmax is proposed and the magnetic memory method for detecting the tensile fatigue damage of the cladding layer by plasma spray welding is discussed.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG441.7

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