风机叶片氧乙炔热喷焊Ni基WC复合涂层工艺及性能研究

发布时间：2018-06-04 23:27

本文选题：氧乙炔热喷焊 + 风机叶片　；参考：《陕西科技大学》2017年硕士论文

【摘要】：风机作为能源矿山等领域重要的辅助设备之一,其使用环境恶劣,叶片受腐蚀磨损严重。因此提高风机叶片的使用寿命,对企业的可靠、经济运行有重要的意义。氧乙炔热喷焊Ni基WC因设备简单、适应性强、效果显著,能够在修复受损失效叶片的同时提高其耐磨耐蚀性能,提高使用寿命,降低生产成本。但是氧乙炔热喷焊Ni基WC因自身设备及工艺特点,涂层易出现孔隙、夹杂、过熔及氧化等问题。本文在综合国内外学者研究的基础上,通过对比不同前处理方法、喷焊工艺参数及WC含量,分析其对涂层的表面沉积、组织缺陷、物相结构、显微硬度、摩擦磨损及耐蚀性能方面的影响,并运用激光重熔及硼硅共渗来改善喷焊后的涂层组织,提高喷焊层的性能。结合实验和测试分析结果,得到如下结论:(1)前处理可以提高喷涂粉末的沉积率,各因素的影响比重大小为:表面粗糙度喷涂距离预热温度,经优化后火焰喷涂的沉积率为43.97%。微观组织结构显示喷涂粉末的沉积方式主要为球状粘连和片层堆积,当片层堆积为主时涂层的效果最好。通过对失效后的风机叶片使用80目的砂纸毛化处理、表面清理、及300℃温度下预热处理后,使用含量35%WC的Ni基合金,用中性火焰在喷涂距离为10~15cm,重熔时间为4min,完成受损叶片的修复,获得0.65mm厚冶金结合的Ni基WC喷焊层,通过微整形加工及喷漆后装机再使用。(2)Ni基WC涂层主要以g-Ni及FeNi_3相为主,NiCrBSi-35%WC表面硬度为856HV,在距离涂层表面0.2mm左右时硬度值达到最大为921HV。WC比例较高时,WC容易因缺少Ni基层的保护,而使涂层表层的WC受热影响脱碳,W元素分布均匀。而涂层内部的WC因分解较少,W元素分布呈现阶梯性变化。W元素在基体中扩散,使C元素相分布集中,Cr3C2、(Cr,Fe)7C3以及(Cr,Fe)23C6等碳化物相增多,而Si、B相的含量在除氧造渣中因过氧化而减少。(3)当WC含量比例提高,虽然涂层的硬度增加,但涂层的孔隙和夹杂增多,出现粉末团聚现象问题也增多,而且直径大于40mm的大孔隙多出现在粉末团聚处。WC含量大于35%时,涂层的磨损易使硬质相颗粒整体脱离,且耐腐蚀性能也较低,WC颗粒也更容易因基体被腐蚀而整体脱离,其中WC含量在30%~40%时耐磨性能较好。(4)重熔时间越长,WC的XRD衍射峰强越低,分解越严重,Cr3C2以及(Cr,Fe)23C6的峰强随着重熔时间延长而增大,Ni_3B及Ni Si相的峰强随重熔时间增加而降低,涂层的氧化越严重。重熔后涂层的摩擦系数在0.3~0.6区间波动,重熔2min时平均摩擦系数为0.45,4min时为0.31,重熔6min时为0.28。重熔时间越长,涂层表面越平整,孔隙度越低,但是过熔氧化的问题也越严重。(5)氧乙炔热喷焊NiCrBSi-WC涂层的缺陷主要有:微缩孔、大孔隙、夹杂、凹凸面、过熔及氧化。通过激光重熔改性后气孔、紧缩孔和夹杂减少,涂层整体较为平滑致密,2q=44°附近Ni2.9Cr0.7Fe0.36和FeNi_3的XRD主峰峰强明显增高,(1 1 1)晶面上相位峰及51.4°和75.6°次强峰出现尖锐化,晶体呈等轴晶区生长,结晶度提高。激光的热效应使Cr3C2、(Cr,Fe)7C3等碳化物相增多,硬度增大,表面硬度提高到909HV,平均摩擦系数降低至0.583。硼硅共渗使涂层的Ni_3B、NiSi等硼化物及硅化物相增多,摩擦系数进一步降低至0.428,抗磨损性能提高1.17倍。
[Abstract]:As one of the important auxiliary equipment in energy mines and other fields, the air fan is used in bad environment and the blade is corroded and worn seriously. Therefore, it is of great significance to improve the service life of the blade of the fan, and it is of great significance to the reliability and economic operation of the enterprise. The oxygen acetylene thermal spray welding Ni based WC has the advantages of simple equipment, strong adaptability and remarkable effect, and can be used to repair the loss effect leaves. The film can improve its wear resistance and corrosion resistance, improve the service life and reduce the cost of production. However, because of its own equipment and process characteristics, the coating of Ni based WC is easy to appear pores, inclusions, over melting and oxidation. On the basis of comprehensive research at home and abroad, the parameters of spray welding process and W are compared by comparing different pretreatment methods. The effect of C content on the surface deposition, microstructure defect, phase structure, microhardness, friction and wear and corrosion resistance of the coating was analyzed, and laser remelting and borosilicate were used to improve the structure of the coating after spray welding and improve the performance of the spray welding layer. The following conclusions were obtained by combining the experimental and test results: (1) pre treatment can improve the spray. The deposition rate of powder coating, the proportion of the influence of each factor is: surface roughness spraying distance preheating temperature, after optimization, the deposition rate of flame spraying is 43.97%. microstructure shows that the deposition of spray powder is mainly spherical adhesion and lamellar accumulation, when the layer accumulation is the best coating, through the failure after the failure. After 80 purpose sand paper hairy treatment, surface cleaning, and preheating treatment at 300 C, the fan blade uses a Ni base alloy with 35%WC content, using neutral flame at 10~15cm and remelting time of 4min to complete the repair of damaged blade, and obtain Ni based WC spray welding layer with 0.65mm thick metallurgical bonding, through micro plastic processing and after spray painting. (2) (2) the main Ni based WC coating is mainly g-Ni and FeNi_3, the surface hardness of NiCrBSi-35%WC is 856HV, the hardness of the coating is higher than that of the coating on the surface of the coating. When the maximum of the hardness is higher than the 921HV.WC ratio, WC is easy to avoid the protection of the Ni base, so that the WC heating shadow of the coating surface is decarbonization and the distribution of the W elements is uniform. The distribution of W elements is less, the distribution of W elements shows a step change, and the diffusion of.W elements in the matrix makes the phase distribution of C elements concentrated, Cr3C2, (Cr, Fe) 7C3 and (Cr, Fe) 23C6 and other carbides increase, while Si, the content of the B phase decreases because of peroxidation in deoxidization slag. (3) the increase in the proportion of the content, although the hardness of the coating increases, but the pores and inclusions in the coating increase The phenomenon of powder agglomeration is also increasing, and when the large pore size larger than 40mm is more than 35%, when the content of.WC in the powder agglomeration is more than 35%, the wear of the coating will easily disconnect the hard phase particles, and the corrosion resistance is low, and the WC particles are more easily disconnected because the matrix is corroded, and the wear resistance of the WC content in 30%~40% is more than that of the matrix. (4) the longer the remelting time, the lower the XRD diffraction peak of WC, the more serious the decomposition, the increase of the peak strength of Cr3C2 and (Cr, Fe) 23C6 with the prolongation of remelting time. The peak strength of Ni_3B and Ni Si phase decreases with the increase of remelting time, and the oxidation of the coating is more serious. The friction coefficient of the coating is fluctuated in the 0.3~0.6 interval and the average friction coefficient of the remelting 2min. For 0.45,4min 0.31, the longer the remelting time for remelting 6min, the longer the 0.28. remelting time, the more smooth the coating surface and the lower the porosity, but the more serious the problem of the oxidation is. (5) the defects of the oxygen acetylene thermal spray welding are mainly micro shrinkage holes, macropores, inclusions, concave and convex surfaces, over melting and oxidation. The pores, holes, and clips after remelting by laser remelting are used. The coating overall is more smooth and compact, the peak intensity of XRD peak in Ni2.9Cr0.7Fe0.36 and FeNi_3 near 2q=44 degree is obviously increased. (111) the phase peak and the 51.4 degree and 75.6 degree peak of the crystal face sharpening, the crystal growth and the crystallinity increase. The thermal effect of the laser increases the carbide phase, such as Cr3C2, (Cr, Fe) 7C3, and the hardness increase. The surface hardness is increased to 909HV, the average friction coefficient is reduced to 0.583. borosilicate, and the Ni_3B, NiSi and other borides and silicides in the coating increase, the friction coefficient is further reduced to 0.428, and the wear resistance is increased by 1.17 times.
【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4

【参考文献】