复合镀层是一种具有特殊功能的新型镀层复合材料，它既具有基质金属的优良特性，又具有分散微粒的特殊功能特点。本文通过化学复合镀和复合电沉积的方法，选取微米级和纳米级ZrO2颗粒为增强相，Ni为镀层基质金属，在Q235碳钢基体上分别制备出Ni-P-ZrO2微米复合镀层和Ni-ZrO2纳米复合镀层。研究了镀液中ZrO2颗粒的加入量和搅拌速率与复合镀层的性能之间的关系，确定了镀液中ZrO2颗粒的最佳添加浓度；利用光学显微镜、扫描电镜(SEM)、能谱仪(EDS)和X-ray衍射仪(XRD)等手段对复合镀层的截面形貌、化学成分和相结构进行了观察和分析。结果表明，ZrO2颗粒均匀地分布于整个Ni-P基质镀层内，界面镀层与基体界面清晰，且结合比较紧密。整个复合镀层平整均匀，厚度约55μm左右。镀态下复合镀层的物相为非晶态结构；当镀液中ZrO2颗粒含量达到9g/L时，镀层颗粒含量和镀速均达到最大，分别为14.3wt.%和21.2μm/h；添加ZrO2粒子能显著提高复合镀层耐蚀性、硬度和耐磨性，复合镀层经热处理以后，镀层有明显的晶化现象，析出Ni3P等硬质相，镀层硬度上升，经400℃热处理硬度达到最大，耐磨性最好。 研究了表面活性剂对纳米ZrO2复合电镀液悬浮分散性的影响，探讨了电沉积过程中搅拌方式对镀层纳米颗粒分散性的影响。结果表明，采用结构复杂的非离子分散剂使纳米ZrO2在电镀液中具有较好的悬浮分散性。在纳米复合电沉积过程中，采用机械+间接超声搅拌沉积的搅拌方式能使镀层中的ZrO2颗粒以接近纳米尺寸的粒径大小分布于Ni基合金中。采用氧化增重的方法重点研究了Ni-ZrO2纳米复合镀层的高温抗氧化性能，并对氧化前后的微观形貌和显微组织进行了观察和分析。结果表明，经800℃以上高温氧化时，纳米复合镀层的高温产物主要为具有小平面化特征的NiO，这些NiO互相连在一起形成一层致密的氧化膜，对基体起到了很好的保护作用。纳米ZrO2镶嵌于镍基质中，一方面阻碍了高温条件下氧在镀层中的扩散，降低了复合镀镍层的氧化速度，另一方面可以阻止Ni2+晶界的短路扩散，从而阻止了氧化过程中晶粒长大，同时由于微粒在镀层表面的均匀弥散，使得基质镀层(Ni镀层)与氧化介质接触的有效面积减少，从而使镀层氧化增重明显降低。此外，由于复合镀层氧化层晶粒尺寸比纯镍镀层的要小，即变形率极大提高。因此，高温循环氧化时，复合镀层的氧化层可通过其扩散蠕变释放热应力。在整个热循环过程中，NiO层的生长是通过O2-(氧化初时可能由部分O2-)的内扩散从表面向内层进行的。

Composite coating is a new kind of composite materials with special function, which has excellent characteristics of the metal matrix as well as special features scattered particles. In this paper, Ni-P-ZrO2 microcomposite coatings and Ni-ZrO2 nanocomposite coatings were prepared on low carbon steel (Q235) substrates by electrolessdeposition and electroplating. The effects of ZrO2 concentration in bath and stirring rate on properties of composite coatings were studied. And the optimal ZrO2 concentration in solution was fixed. The surface and cross-sectional micrographs of the composite coatings were observed with optical microscope and scanning electron microscopy (SEM). And the chemical composition and phase transformation of composite coatings were analyzed with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). It was shown that a relatively uniform concentration of ZrO2 particles along the cross section of electroless Ni-P-ZrO2 composite coatings, and the continuous and uniform composite coatings with about 55μm of thickness showed good adhere to substrate. The structure of Ni-P-ZrO2 composite coatings as deposited was amorphous. When the ZrO2 concentration in solution ascend to 9g/L, particles content in coating and deposition rate reached the maximum, 14.3wt.% and 21.2μm/h, respectively. The presence of ZrO2 particles can enhance significantly microhardness、corrosion resistance and wear resistance performances of Ni-P alloy. After heat-treated, the matrix of composite coatings crystallized into nickel crystal and nickel phosphide(Ni3P), which result in an increase in the coating hardness, with a maximum hardness and excellent tribological behavior being achieved after annealed at 400°C. The effects of different kinds of dispersants on nano-ZrO2 composite electroplating bath as well as effects of stirring means in plating process on dispersion of nano-ZrO2 in composite coatings were studied. It was shown that the ZrO2 suspension which was added to the dispersant 752W with complex structure had better dispersion and stability. The mechanical stirring+intermittent ultrasonic had obvious stirring scatteredrole，strengthen and promoting role and refining the nickel grains. The oxidation resistance of the coatings was discussed by their weight gains in a muffle furnace. It was shown that the products of nanocomposite coatings consist of NiO with trait of small plane after high temperature oxidation over 800°C. These NiO which linked to each other to form a dense oxide film played a very good protection to the substrate. The reason why the Ni-ZrO2 nano-composite coatings can improve the high temperature oxidation resistance maybe that the rate-controlling Ni2+ diffusion along short-circuit paths is blocked by embedded nano-ZrO2 particles that originally existed in the Ni-ZrO2 nanocomposite coatings, which exerted a reactive-element effect on the growth of NiO scales on the composite coatings. What is more, the disperation of ZrO2 particles in the Ni-P matrix reduces the effective area of Ni alloy contacting with ambient oxygen, thus significantly decreasing weight grains of the composite coating. In addition, oxide layer grain size of nanocomposite coatings was smaller as compared with pure nickel coating, which can greatly enhance the deformation rate. During the circulating oxidation process, oxide layer of nanocomposite coatings can be released by the diffusion creep thermal stress. The growth of NiO layer was formed through the O2- inner diffusion (oxidation initially may be caused by some O2-) from the surface to the internal nanocomposite coatings.