钻井泵缸套激光熔覆镍基陶瓷梯度涂层研究

发布时间：2018-07-23 08:15

【摘要】：钻井泵作为钻井系统的核心,其能否正常工作关系整个钻井过程。钻井泵中最容易损伤的零部件为缸套,进入柱塞与缸套之间的硬质颗粒在运动过程中会对缸套内壁造成磨损,其磨损机制主要是磨粒磨损。激光熔覆制备Ni基WC涂层可以将合金良好的韧塑性能与陶瓷的耐磨性能结合在一起。但WC与Ni基合金的物相差异,使熔覆层中存在较大的应力,最终导致熔覆层的开裂。制备梯度涂层可以缓解熔覆粉末与基体之间因物相差异所导致应力集中。本文主要通过激光熔覆的方式来制备高含量WC镍基涂层。通过优化激光熔覆工艺参数,引入CaF2和Ni35过渡层来有效解决裂纹问题。利用扫描电镜观察熔覆层的微观组织,测试其力学性能,最终得到性能良好的超硬熔覆层。研究结果表明,单道熔覆层中随着WC含量的增加,熔覆层的裂纹率先升高后下降,在WC含量为30%左右时达到最大值;为保证熔覆层的成型性和耐磨性能,最终确定SD-Ni45作为基础熔覆材料,其最佳工艺参数:激光熔覆功率3500W,扫描速度100mm/min;通过对超硬涂层的微观组织和物相分析可知超硬涂层中主要包括WC和碳化物以及树枝状组织γ-Ni,由于熔覆层中含有较多的WC,其显微硬度可达2000HV0.1。在超硬涂层中添加5%CaF2可以改善熔覆层的表面成型,同时CaF2密度低在激光熔覆过程中向熔覆层表面运动,对熔池起到搅拌的作用促进WC在熔覆层中均匀分布,这种组织和硬质相的均匀分布使其显微硬度有所下降仅有1500HV0.1,但其耐磨性有明显提高;在超硬涂层与基体之间增加一层Ni35过渡层可以缓解因超硬涂层与基体物相差异而产生的应力集中,同时Ni35过渡层显微硬度介于二者之间避免了熔合区处显微硬度的陡降,使整个熔覆层的显微硬度过渡平缓。最终得到了成型良好、无裂纹且组织致密的梯度涂层。
[Abstract]:As the core of drilling system, the drilling pump is the core of the drilling system. The most easily damaged parts in the drilling pump are cylinder sleeve. The hard particles between the plunger and the cylinder sleeve will wear out on the inner wall of the cylinder liner during the movement process. The wear mechanism is mainly abrasive wear. The laser cladding is used to prepare the Ni based WC coating. The good toughness and ductility of the alloy are combined with the wear resistance of the ceramics. But the difference between the WC and the Ni based alloys makes the cladding layer more stress and eventually leads to the cracking of the cladding layer. The preparation of the gradient coating can relieve the stress concentration in the difference between the powder and the matrix. This paper mainly through laser cladding. The high content WC nickel base coating was prepared by the method of optimizing the laser cladding process parameters and introducing the transition layer of CaF2 and Ni35 to solve the crack problem effectively. The microstructure of the cladding layer was observed by scanning electron microscope, and the mechanical properties of the cladding layer were tested. Finally, the super hard cladding layer was obtained. The results showed that the content of WC in the single channel cladding layer was with the content of the cladding. The cracks in the cladding layer first rise and then decrease and reach the maximum when the content of WC is about 30%. In order to ensure the formability and wear resistance of the cladding layer, the SD-Ni45 is finally determined as the basic cladding material, and the optimum technological parameters are the laser cladding power 3500W, the scanning speed 100mm/min, and the microstructure and phase separation of the superhard coating. It is known that the superhard coatings mainly include WC, carbide and dendritic tissue gamma -Ni. Because of the more WC in the cladding layer, the microhardness of the coating can reach 2000HV0.1. in the superhard coating by adding 5%CaF2 to improve the surface formation of the cladding layer. At the same time, the density of CaF2 is low in the laser cladding process to the surface of the cladding layer, and the weld pool is stirred. The mixing effect promotes the uniform distribution of WC in the cladding layer. The uniform distribution of the microstructure and hard phase makes the microhardness decrease only 1500HV0.1, but its wear resistance is obviously improved, and a layer of Ni35 transition layer between the superhard coating and the matrix can relieve the stress concentration caused by the difference between the superhard coating and the matrix, and N The microhardness of the i35 transition layer between two avoids the steep drop of microhardness at the fusion zone and the transition of the microhardness of the whole cladding layer slowly. Finally, a gradient coating with good shape, no crack and dense tissue is obtained.
【学位授予单位】：中国石油大学(华东)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG174.453

【参考文献】