【作者】 王军丽；

【导师】 龙晋明；

【作者基本信息】 昆明理工大学 ， 材料学， 2003， 硕士

【摘要】 本文阐述了目前国内外Ni-B、Ni-W、Ni-W-B等复合镀层研究现状，在此基础上，作者提出了一种利用脉冲电沉积来制取RE-Ni-W-B复合镀层的新方法。此外，通过在RE-Ni-W-B体系中添加PTFE、BN、MoS₂、SiC、B₄C、Al₂O₃固体颗粒，以降低该复合镀层的内应力，消除复合镀层的表面裂纹，并提高复合镀层的硬度及耐磨性等性能。 阐述了合金共沉积、复合电沉积理论及脉冲电沉积RE-Ni-W-B系工艺的沉积机理，并借助于W-H₂O系电位-pH图、B-H₂O系电位-pH图、Ni-B-H₂O系电位-pH图，从热力学角度探讨了电沉积RE-Ni-W-B系复合镀层的可能性以及难易程度。 采用正交实验方法研究了直流电沉积RE-Ni-W-B工艺，通过对复合镀层硬度及沉积速度的分析，筛选出了最佳的工艺条件。但由于镀层脆性较大，复合镀层表面裂纹众多。 在确定出直流电沉积最佳工艺条件的基础上，又采用脉冲电沉积的方法来制取RE-Ni-W-B多元复合镀层，降低了复合镀层的内应力，减少了镀层的表面裂纹，同时提高了复合镀层的硬度及耐磨性，得出了脉冲复合电沉积RE-Ni-W-B的最佳脉冲频率及占空比，但该复合镀层的表面裂纹仍很明显。 研究了SiC、B₄C、Al₂O₃等硬质耐磨固体颗粒及PTFE、BN、MoS₂等减摩微粒对脉冲电沉积RE-Ni-W-B复合镀层性能的影响。实验表明，在这些颗粒共沉积的同时，降低了其它品粒的尺寸，而且镀液中这些颗粒含量越多，沉积的晶粒尺寸就越小。因此，这些颗粒的使用，彻底消除了复合镀层的表面裂纹，提高了镀层表面的光滑度。 通过成份分析表明，与直流电沉积相比，采用脉冲电沉积的方法能提高RE-Ni-W-B多元复合镀层中W和B的含量。镀液中所添加的SiC、B₄C、Al₂O₃、PTFE、BN、MoS₂颗粒在镀层中均有不同程度的沉积，但又会对镀层中W和B的含量产生影响。 对RE-Ni-W-B-MoS₄-B₄C和RE-Ni-W-B-PTFE-B₄C两种复合镀层的相结构进行了分析，结果表明，RE-Ni-W-B-MoS₂-B₄C复合镀层镀态下以非晶态为主，部分已晶化；当经500℃热处理后，镀层已晶化；经800℃热处理后，CeO₂和B₄C仍以化合物的形式存在。而RE-Ni-W-B-PTFE-B₄C复合镀层在镀态下介于非晶与微晶之间；200℃热处理后，镀层状态绍毋Z梦/又一贷硬子一学夕z甘丈卿岁变为微晶;400℃热处理后，PTFE的特征峰线强度变弱;600℃热处理后复合镀层完全品化，合金的原子排列规则，PTFE完全分解;经800℃热处理后，CeOZ和B汇仍以化合物的少侈式存在。 通过对复合镀层硬度、磨损率及高温抗氧化性的比较分析，研究了SIC、氏C、A12认三种不同的硬质颗粒对RE一Ni一W一B一PFTE、RE一Ni一W一B一BN及RE一Ni一W一B一MOS，复合镀层性能的影响。含有SIC、B不、A12O:、的RE一Ni一w一B复合镀层性能优异，硬度明显高于不加含固体颗粒时RE一Ni一W一B复合镀层，磨损率也显著低于RE一Ni一W一B复合镀层。并得出在脉冲电沉积获得的RE一Ni一w一多元复合镀层中，在添加PTFE、BN、MoSZ三种物质中，自润滑性能最好的是PTFE。更多还原

【Abstract】 The current research status of Ni-B, Ni-W, Ni-W-B composite coatings at home and in abroad is discussed in this thesis, and the author puts forward a new method to obtain RE-Ni-W-B multifunctional composite coatings by means of pulse electrodeposition. Furthermore, some grains of PTFE, BN, MoS2, SiC, B4C, and A12O3 are added into the RE-Ni-W-B system to reduce its internal stress, eliminate its surface cracks and enhance its hardness, wear-resistance and the resistance to oxidation at high temperature.The theories of alloy co-deposition and composite electrodeposition and the mechanism of pulse electrodeposition of RE-Ni-W-B coatings are expounded. By use of E-pH patterns of W-H2O, B-H2O and Ni-B-H2O, the possibility of electrodeposition of RE-Ni-W-B composite coatings is discussed from the standpoint of thermodynamics.Through analysis of hardness and thickness of the composite coatings, the optimal process conditions of DC electrodeposition of RE-Ni-W-B composite coatings are screened out by orthogonal experiment. But there are many cracks on the surface of RE-Ni-W-B composite coatings owing to high internal stress.After determining the optimal process conditions of DC electrodeposition of RE-Ni-W-B composite coatings, the composite coatings are also obtained by means of pulse electrodeposition so as to decrease the internal stress, eliminate the cracks and enhance the hardness and wear-resistance of the coatings. The best pulse frequency and duty cycle are obtained, but the surface cracks of composite coatings are still obvious.The effects of wear-resistant grains such as SiC, B4C, AI2O3 and antifriction grains such as PTFE, BN, MoS2 on the properties of pulse electrodeposited RE-Ni-W-B multifunctional composite coatings are studied. Experimental results indicate that the sizes of other crystalline grains decrease during the co-deposition of these grains, and the higher the contents of these grains in the bath are, the smaller the sizes of other crystalline grains. The surface cracks of the RE-Ni-W-B composite coatings are eliminated and the smoothness is improved owing to the uses of these grains.The composition analysis shows that pulse electrodeposition can increase W and B contents in the RE-Ni-W-B composite coatings, compared with DC electrodeposition. All ofthese solids such as SiC, B4C, AI2O3, PTFE, BN, MoS2 can deposit into the RE-Ni-W-B composite coatings to a different degree, but this will affect W and B contents in the coatings.The X-ray diffraction results of RE-Ni-W-B-B4C-MoS2and RE-Ni-W-B-PTFE-B4C composite coatings show that (1) As to the RE-Ni-W-B-B4C-MoS2 composite coating, the coating is mainly amorphous and partially crystallized as-deposited, and the coating is been crystallized after heat treatment at 500. (2) As to the RE-Ni-W-B-PTFE-B4C composite coating, the coating is between amorphous and micro-crystalline as-deposited, and the coating changes into micro-crystalline state after heat treatment at 200; the diffraction peak of PTFE decreases after heat treatment at 400; PTFE begins to decompose and the composite coating is crystallized after heat treatment at 600. CeO2 and B4C in the RE-Ni-W-B-B4C-MoS2and RE-Ni-W-B-PTFE-B4C composite coatings are very stable and do not decompose after heat treatment at 800 .Through analysis and comparison of the hardness, wear rate and the resistance to oxidation at high temperature of the composite coatings, the effects of three different grains SiC, B4C, AI2O3 on the properties of pulse electrodeposited RE-Ni-W-B-PFTE, RE-Ni-W-B-BN and RE-Ni-W-B-MoS2 multifunctional composite coatings are studied. The results indicate that the properties of the multifunctional composite coatings including SiC, B4C, AI2O3 grains are much better than those of the coatings without these grains, the hardness improves and the wear rate decreases obviously. The results also indicate that the best self-lubricating material is PTFE in the RE-Ni-W-B composite coatings obtained by pulse electrodeposition.更多还原