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采用超音速火焰喷涂技术(HVOF)在3种丙烷流量(30,36和42 L/min)下将机械球磨后的TiB_2-25Ni颗粒沉积在Q235钢表面上获得不同涂层,将涂层在600℃(50次、100次、150次)和800℃工况下进行热震试验,研究涂层的抗热震性能。采用扫描电镜(SEM)表征热震后涂层的表面和截面形貌以分析热震后的裂纹产生和扩展情况,通过X射线衍射技术(XRD)分析热震后涂层的物相演变规律。研究结果发现,3种涂层在600℃热震条件下随着热震循环次数的增加,涂层中裂纹扩展的愈加严重,且在热震150次后出现了纵向和横向裂纹,并且以丙烷流量为36 L/min时涂层失效最快。通过在800℃涂层热震后发现,涂层失效更快,涂层热震循环次数明显降低,并且在涂层表面出现了明显的网状式裂纹,在涂层截面中裂纹扩展的更为强烈,并延伸至涂层和基体的界面处,从而导致腐蚀介质(水或空气)进入至裂纹中使基体腐蚀,在交界处产生了明显的腐蚀产物。通过对涂层在不同热震条件后的XRD分析发现,3种涂层的主要物相仍然是TiB_2和Ni,热震后涂层表面氧化物增多。
TiB 2 - 25Ni particles, which had been mechanically ball milled, were deposited on the surface of Q235 steel with three different propane flow rates (30, 36 and 42 L / min) using a supersonic flame spray technique (HVOF) (50 times, 100 times, 150 times) and 800 ℃ under the conditions of thermal shock test to study the thermal shock resistance of the coating. The surface and cross-sectional morphology of the post-thermal shock coating were characterized by scanning electron microscopy (SEM) to analyze the crack growth and propagation after thermal shock. The phase evolution of the post-thermal shock coating was analyzed by X-ray diffraction (XRD). The results show that with the increase of the number of thermal shock cycles under 600 ℃ thermal shock, the crack growth of the three coatings becomes more and more serious, and longitudinal and transverse cracks appear after thermal shock for 150 times, The coating failed most rapidly at 36 L / min. After thermal shocking at 800 ℃, the failure of the coating was found to be faster and the number of thermal shock cycles significantly decreased. Moreover, a clear net-like crack appeared on the coating surface and the crack propagation in the coating cross-section was more Strongly and extending to the interface between the coating and the substrate, causing corrosive media (water or air) to enter the crack causing the substrate to erode, producing significant corrosion products at the interface. By XRD analysis of the coatings under different thermal shock conditions, the main phases of the three coatings are still TiB_2 and Ni, and the oxides on the surface of the coatings increase after thermal shock.