激光熔覆原位合成碳化钨增强镍基表面复合材料的研究

发布时间：2018-01-20 16:39

本文关键词： 激光熔覆原位自生碳化钨镍基复合涂层耐磨性　出处：《广东工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：金属基陶瓷复合涂层既有金属的强韧性,又有陶瓷材料良好的耐蚀性、耐高温性、耐磨性和抗氧化性。采用原位自生技术制备金属基陶瓷涂层,增强体可以在制备过程中通过原位反应生成,增强体尺寸细小,分布弥散,表面无污染,与金属基体浸润性好,可改善增强体与粘接金属之间的界面结合。本文研究了采用不同配比的Ni25/(WO3+C)复合粉体原位自生的涂层的微观组织、物相组成、涂层脆性、显微硬度、摩擦磨损等性能的变化规律,并深入分析了磨损机理。通过电子显微镜(SEM)、X射线衍射仪(XRD)、显微硬度测试仪、WS-2005涂层附着力自动划痕仪、CFT-I型多功能材料表面综合性能测试仪等仪器手段研究了涂层的组织和性能。研究结果表明：(1)涂层预置粉末的厚度选用1.5mm,最佳的工艺参数为：电流为300A,脉宽为1.6ms,频率为30Hz,速度为2mm/s。稀释率较低,涂层与基体熔覆良好表面光滑平整,宏观形貌优异,涂层厚度为200-300μm。(2)涂层的顶部组织大多为细小枝晶和细小等轴晶；涂层的中部为方向各异的树枝晶和胞状晶；底部为平面晶。枝晶的生长方向垂直于平界面,平行于激光熔覆的传热方向。复合涂层主要由(Fe)Ni固溶体、Cr7C3、 Cr23C6、 Fe3W3C、W2C、 WC等物相所构成。WxC的大小约为0.5-2μmm,形态呈颗粒状、长方形、三角形等状。原位自生的WxC颗粒无缺陷,WxC内部未发生开裂,且WxC与周围基体结合良好。(3)涂层的硬度明显高于基体的硬度；并且随着(W03+C)含量增加,复合涂层的显微硬度也逐渐上升。最高硬度达704HVo.2,约为基体的3.5倍。(4)相比45钢基体,涂层的摩擦系数较低,当复合粉体中(W03+C)含量低于40%时,摩擦系数随(W03+C)含量的增加而逐渐降低；(W03+C)含量上升到50%时摩擦系数反而上升。(WO3+C)含量为40%时摩擦系数与高铬铸铁耐磨钢Crl5Mo3的摩擦系数相近,取到了很好的减摩作用。(5)10%-30%(W03+C)的涂层的磨损区域存在一些凹坑和磨屑,主要磨损机理为粘着磨损和磨粒磨损；40%(WO3+C)和50%(W03+C)的涂层的磨损区域存在一些磨屑和微裂纹,磨损机理主要为磨粒磨损和脆性剥落。(6)利用激光辐照,在Ni25、WO3、Al和C粉末之间发生铝热反应原位合成WxC复合涂层。反应产物物相组成为WC、W2C、W3C、和Al2O3相,WxC相为白色颗粒状,尺寸小于200nm,主要分布在(Fe)Ni固溶体的晶界上,也有部分分布在晶内。熔覆层组织均匀致密、无裂纹和孔洞等缺陷,熔覆层与基体呈良好的冶金结合。熔覆层最高硬度为900HVo.2,是基体的4.5倍。
[Abstract]:The metal-based ceramic coatings were prepared by in-situ in-situ technique. The composite coatings not only have the strength and toughness of metals, but also have good corrosion resistance, high temperature resistance, wear resistance and oxidation resistance of ceramic materials. The reinforcements can be produced by in-situ reaction in the process of preparation. The reinforcements are fine in size, dispersed in distribution, free of surface pollution, and have good wettability with metal matrix. In this paper, the microstructure, phase composition and brittleness of in-situ Ni25/(WO3 C composite powder coating were studied. The variation of microhardness, friction and wear, and the wear mechanism were analyzed. The SEM X-ray diffractometer and the microhardness tester were used. WS-2005 coating adhesion automatic scratch instrument. The microstructure and properties of the coating were studied by means of CFT-I multifunctional material surface comprehensive performance tester and other instruments. The results showed that the thickness of the coating preset powder was 1.5mm. The optimum technological parameters are as follows: current is 300A, pulse width is 1.6 Ms, frequency is 30 Hz, speed is 2 mm / s. The dilution rate is low, and the surface of coating and substrate is smooth and smooth. The microstructure of the coating is mostly fine dendrite and fine equiaxed crystal. The central part of the coating is dendritic and cellular crystal with different directions. The growth direction of the dendrite is perpendicular to the flat interface and parallel to the heat transfer direction of laser cladding. The composite coating is mainly composed of Cr7C3 and Cr23C6. The size of Fe _ 3W _ 3C _ 2C _ 2C and WC is about 0.5-2 渭 mm. The shape of Fe _ 3W _ (3C) W _ (2C), W _ (2C), WC and so on is granular, rectangular and triangular. There is no defect in in-situ WxC particles. There was no cracking in WxC, and the hardness of WxC coating was obviously higher than that of substrate. With the increase of W03 C) content, the microhardness of the composite coating increases gradually, and the highest hardness is 704HVo.23.5 times as much as that of the substrate. The friction coefficient of the coating is lower, when the content of W03 C in the composite powder is lower than 40%, the friction coefficient decreases with the increase of W03 C content. When the content of W03 C increased to 50, the friction coefficient increased. When the content of WO 3 C was 40, the friction coefficient was similar to that of high chromium cast iron wear resistant steel Crl5Mo3. There are some pits and debris in the wear zone of the coating. The main wear mechanism is adhesive wear and abrasive wear. There are some debris and microcracks in the wear zone of the WO _ 3 C and 50 W _ 03 C) coatings. The wear mechanism is mainly abrasive wear and brittle spalling. WxC composite coatings were synthesized in situ by aluminothermic reaction between Ni _ (25) O _ (3) O _ (3) Al and C powders. The reaction products were composed of WCC _ (2) C _ (2) C _ (3) C and Al2O3 phase. The WxC phase is white granular with a size less than 200nm.It mainly distributes on the grain boundary of Fegni solid solution, and also has some distribution in the crystal. The microstructure of the cladding layer is uniform and dense, and there are no defects such as cracks and pores. The highest hardness of the cladding layer is 900HVo. 2, 4.5 times of that of the substrate.
【学位授予单位】：广东工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG174.4

【参考文献】