铝合金存在硬度低、耐磨性差、容易发生晶间腐蚀等问题而使其应用受到限制。在铝合金表面上形成复合镀层是解决以上问题非常有效的途径之一。复合镀层是一种具有优良性能且功能特殊的新型复合材料，它能显著提高镀层的硬度和耐磨性。β-SiC具有很好的化学稳定性、抗磨、耐高温、耐热震、耐腐蚀等性能，是理想的第二相增强颗粒。在多种材料制备、加工工艺以及表面处理技术中，添加适量的稀土元素能够显著地改善工艺条件、降低生产成本并提高产品性能。本文以提高铝合金表面综合性能为目的，通过化学复合镀技术在铝合金基体表面制备了性能优异的Ni-P-β-SiC复合镀层，重点研究了稀土对Ni-P非晶镀层和Ni-P-β-SiC复复合镀层性能的影响。采用光学显微镜、X射线衍射仪、扫描电镜(SEM)和能谱仪(EDS)、划痕仪、显微维氏硬度仪等多种检测手段对复合镀层的微观形貌、元素分布、结构性能等做了表征和分析，主要研究内容和结果如下。 (1)研究了镀液中β-SiC微粉的添加量与Ni-P-β-SiC复合镀层力学性能之间的关系，确定了β-SiC微粉的最佳添加浓度。研究结果表明：添加β-SiC微粉能显著提高复合镀层的硬度和耐磨性，当加入镀液中β-SiC微粉的浓度为10g/L时，所得Ni-P-β-SiC复合镀层综合性能最佳，此时镀层与基体界面清晰且结合良好，β-SiC微粉均匀弥散于Ni-P基质合金镀层内，整个镀层平整光滑，没有裂纹等缺陷，沉积速率、硬度均达到最高，分别为14.2μm/h和580HV0.05，磨损量比相同试验条件下Ni-P非晶镀层磨损量降低了1.6倍，摩擦系数降低为0.5，耐磨性得到显著提高。 (2)研究了稀土盐Y(NO3)3和LaCl3对Ni-P非晶态化学镀层微观形貌、沉积速率、硬度和耐蚀性等性能的影响。研究结果表明：两种稀土元素均提高了Ni-P非晶态镀层中P的含量和镀层的非晶化程度，沉积速率、耐蚀性和硬度均有显著提高，Y元素的作用更加显著；当添加150mg/L的Y(NO3)3时，所获得的镀层综合性能最佳，结合力为32.64N，P含量达12.6%，显微硬度达558.6HV0.05，沉积速率为26.5μm/h，耐蚀性显著提高：在3.5%的NaCl溶液中，镀层的腐蚀电位由-0.70V上升到-0.48V，提高了220mV。 (3)重点研究了稀土盐Y(NO3)3对Ni-P-β-SiC复合镀层性能的影响。研究结果表明：在镀液中添加稀土盐Y(NO3)3能提高Ni-P-β-SiC复合镀层的沉积速率、耐蚀性和耐磨性。当稀土盐Y(NO3)3添加浓度为1.0g/L时所获得的Ni-P-β-SiC复合镀层综合性能最佳，沉积速率为15.8μm/h，硬度590HV0.05，耐蚀性能也显著提高：在3.5%的NaCl溶液中，镀层的腐蚀电位由-0.74V上升到-0.57V，提高了170mV。

Although aluminum alloy is widely used, its application is limited for its low hardness, poor wear resistance and easy to inter granular corrosion. Composite coating is a kind of new type composite coating material which have excellent performance and special function. It not only retains excellent characteristics of the matrix metal but also has the characteristics of dispersed particles of special function. The hardness of β-SiC powder is close to the diamond, and it has good chemical stability, wear-resistance, high temperature resistance, heat resistance, corrosion resistance and other excellent properties, which is is the ideal second phase reinforcing particles. In order to improve the surface property of aluminum alloy, this topic successfully prepared and studied the strengthening effect of Ni-P-β-SiC composite coating on aluminum alloy substrate surface through the chemical composite plating method, and further studied the effect of rare earth on the properties of amorphous coating and composite coating. We adopt optical microscope, SEM and EDS, XRD, micro vickers hardness tester to observe and analysis microstructure, element distribution and organization structure in the composite coating. The main research contents and research results were as follows: (1) We study the relationship between the mechanical properties and particles of β-SiC in the plating solution concentration and determine the best concentration of particles of β-SiC. The results show that adding β SiC particles can significantly increase the hardness and wear resistance of composite coating. When the concentration of added β-SiC particles in the plating solution is 10 g/L, the Ni-P-β-SiC composite coating performance is the best. The coating and substrate interface is clear and good, β-SiC particles uniformly dispersion in Ni - P alloy matrix coating. the coating level is smooth, without pores, cracks and other defects, the average speed, hardness and wear resistance are the best, which is 14.2 μm/h and 580 HV. (2) We respectively study the effect the different kinds of rare earth elements (Y/La) and its content to the chemical plating of Ni-P amorphous microstructure, deposition rate, hardness and corrosion resistance, etc. These results show that both kinds of rare earth elements add to improve the P content in Ni - P amorphous coating and coating of the degree of crystallization, has realized the purpose of the deposition rate, coating hardness and corrosion resistance increased significantly, and the effect of Y(NO3)3 is more pronounced. Adding 150 mg/L Y(NO3)3 in the coating is the best comprehensive performance. When the content of P in the coating is 12.6%,the microhardness reach 558.6 HV, deposition rate is 26.5 μm/h. It obtained significantly higher resistance to corrosion in 5% NaCl solution. (3) We focuses on rare earth elements Y to effect Ni-P-β-SiC composite coating performance. The influence of the research shows that Y(NO3)3 can improve the performance of Ni-P-β-SiC composite coating which is include of plating rate, hardness, corrosion resistance and abrasion resistance. When the concentration of Y(NO3)3 to add 1.0 g/L in Ni-P-β-SiC,its omprehensive performance is the best. The deposition rate is 15.8 μm/h, hardness is 590 HV, the performance of corrosion resistant has been improved significantly.