| The thermal spraying technology which as a surface strengthening technology is one of surface engineering technology, and its development and promotion have been given priority in china. With the development of science and technology the thermal spraying technology has been made extensive popularization and application at home and abroad. In order to guarantee the usability of thermal spraying component, people mainly focused on wear resistance, corrosion resistance, high temperature resistant and heat insulation performance, electrical and optical properties, etc. The fatigue performance and affecting factors on fatigue of thermal spraying component were rarely concerned. In this paper, the forming process of thermal spray and the affecting factors of fatigue performance were studied, and some important results were obtained as follow:1. The micro-mechanism of thermal spraying coating forming was analyzed, burning flame characteristics of thermal spraying, speed characteristics of spraying particles, oxidation behavior of spray molten droplets in the process of the flight were researched, the reasonable process scheme and spraying parameters of thermal spraying component were determined.2. The combined bending and torsion fatigue life of the sample which were remelted under different remelting time conditions were investigated by test. The macrofracture and the microfracture of samples, coating composition, limit stress, fatigue extension area were analyzed. The results show that the reasonable remelting time is the key factor to decide the performance of combined bending and torsion fatigue of thermal spraying components. The components have the longest fatigue life when remelting time is reasonable. The shorter remelting time the lower fatigue lifetime resulting from loose coating, lower strength of coating surface and the interface of coating and substrate and SiO2particles produced by unfused Si particles reacted with Oxygen. The longer remelting time the lower fatigue lifetime owing to reproduced particles of SiO2that as the source of crack, and the longer soaking time, the shorter fatige lifetime of components.3. The logarithmic value (lgS) of fatigue crack propagation region area(S) is proportional to logarithmic value(1g N1) of fatigue life of base samples and spraying samples with reasonable remelting time, and the correlation coefficient is0.992and0.994, respectively. Thus it can be inferred that the size of the propagation region area can be used to estimate the fatigue life of samples with reasonable remelting time.4. The main composition of coating with different remelting time are Cr7C3、Ni、 Cr3Ni5Si2、CrB、 Ni3B. The content of different composition of coating surface was changed with different remelting time. The content of hard phase of coating surface was decreased obviously after longer remelting time.5. The coating thickness is another key factor to decide the fatigue life of flame thermal spraying components. The reasonable coating thickness is0.25mm for the designed samples. The stretching and compression fatigue lifetime of flame thermal spraying components was decreased with the increase of the thickness of coating when the thickness of coating is more than0.25mm. The fatigue lifetime of components is closely related to the number and the average size of nonmetallic particles and pores. The interface and the surface of coating endure more loads of stretching and compression than the middle coating when the coating thickness and the remelting time are reasonable, so the stretching and compression fatigue lifetime of thermal spraying samples is longer than matrix samples. The test results show that the research on fatigue lifetime of flame thermal spraying component has practical application value.6. The remelting time is a key factor to decide the wear resistance and surface hardness of coating of thermal spraying components. The surface hardness of coating with remelting time of2min,5min,10min and12min is340HV,385HV,455HV,400HV, respectively, and the corresponding wear volume of coating is3.734X107μm3、3.50974×107μm3、3.029×107μm3、3.266×107μm3, respectively. The test results show that the surface micro-hardness and the wear resistance ability of coating are strongest when the remelting time is reasonable. The wear mechanism of coating is mainly abrasive wear and fatigue wear.7. An energy model for a characterization parameters of energy form that can characterize the fatigue life of low and high cycle fatigue simultaneously was used to forecast the LCF life of thermal spraying components with different remelting time, the predicted results were consistent with the experimental results. The result show that using the law of energy to forecast the fatigue life of coating components can reveal the nature of the fatigue damage, the results has higher accuracy and clear physical meaning, so it has important practical significance to evaluate the life time of cycle fatigue. |
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