【作者】 张涛；

【导师】 温广武；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2008， 硕士

【摘要】 本文采用化学镀法在纳米α-Al₂O₃表面包覆了均匀的镍层,研究施镀参数对镀速和镀层形貌的影响规律。并对制备的复合粉体进行等离子喷涂,分析了喷涂参数对涂层组织结构和涂层性能的影响规律和特点。镀液组成对镀液的稳定性研究表明,络合剂和缓冲剂的种类和用量影响最终施镀质量。最终确定了采用C6H5Na3O7·2H2O（15-20g/l）和EDTANa2（10-15g/l）双络合的镀液明显提高了镀液的稳定性。镀层增重影响因素表明,温度和施镀时间对镀层增重影响明显,装载量对镀层增重影响最小。镀速研究发现,在50-60°C范围内镀速较低,维持在1.0%/min以下;在60-70°C范围内镀速升高明显,但不超过3.0%/min。扫描电镜（SEM）、透射电镜（TEM）分析发现,在70°C时由于镀速显著增大,镀层成针状和片状结构。在55°C时由于镀速较低,镀层光滑、致密。确定了在T=55°C,PH=11.5,t=50min,装载量为20g/l条件下制备的Ni/Al₂O₃复合粉应做等离子喷涂的原料粉,复合粉中Ni含量为10.35wt.%。等离子喷涂实验结果表明,喷涂工艺参数对涂层结构有重要影响。喷涂功率增大,颗粒之间的结合趋向紧密结合,涂层内部气孔减少,但同时Ni的烧蚀变大。涂层耐磨性测试结果表明,在喷涂功率为30kw的喷涂条件下制备的涂层磨损率最低,其值为0.5cm3/N·m。涂层硬度有随喷涂功率增大而升高的规律,在喷涂功率为32.5kw时,涂层硬度达8.8GPa。物相分析测试结果表明,采用化学镀制备的Ni/Al₂O₃复合粉在在相同喷涂条件下α-Al₂O₃向γ-Al₂O₃转变程度要小于机械混合法制备的涂层;涂层中Ni元素的分布要比机械混合法均匀;且在相同喷涂参数下化学镀法得到的涂层表面和内部气孔明显少于机械混合法。更多还原

【Abstract】 In this paper, uniformed nickel coating was fabricated on the surface ofα-Al₂O₃ nano powder, using electroless plating method. The influence of plating parameters on plating rate and coating morphology has been studied. The composite was used as raw material in plasma spraying, and the influence of spraying parameters on coating structure and properties also has been analyzed. The influence of bathing composition on stability of the bath was analyed, and at last, bathing sability was optimized using double reductants of sodium citrate and EDTANa2.Coating weight increasing rate experiment indicated that temperature and plating time have sharp magnificant to weight increasing rate, powder load has the least influence on the parameter. Plating rate experiment reveals that lower plating rate can be obtained at 50-60°C, keeping no more than 1.0%/min. Plating rate increase sharply at the temperature of 60-70°C, reaching to 3.0%/min. Scanning electron microscopy （SEM） and Transmission electron microscopy （TEM） were used to study the coating morphology and found, needle like and plate like coating formed as the plating rate increased when the temperature got up to 70°C. There are no obvious differences in coating morphology and plating rate when the powder load between 10 to 15g/l, and the plating rate increased with the load up to 20g/l. Dense and smooth coating formed at the temperature of 55°C, PH value 11.5 and 50 minutes plated with nickel content of 10.35wt.%, which is agreement to use as raw material of plasma spaying.The results of plasma spraying indicated that the influence of sparying parameters on coating structure was crucial. Experiment results conveyed that granules well-kint, pores decreased and at the same time, nickel ablated highly, when spraying power increased. Coating tribology results that coating frication rate has the lowest value, only 0.5cm3/N·m at the spraying power of 30kw. Coating hardness increases with spraying power higher, and the coating hardness reach to 8.8Gpa, at the spraying power of 32.5kw.X-ray diffracation analized revealed thatα-Al₂O₃ less likely transformed to γ- Al₂O₃ in electroless plating method than mechanical blended method. The EDS indicated that, the distributing of Ni much more uniformed in electroless plaing than mechanical blending method. SEM testing result reveals that there are fewer pores on the coating surface and undersUrface using electroless plating than mechanical method, which is at the same spraying parameters.更多还原