A Study in the Fabrication and Tribology Properties of the Ni-Mo Surface Coating
| Autor: | Tsai,Chun-Chuan, 蔡春泉 |
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| Rok vydání: | 2012 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 100 The goal of this study is to develop Ni-Mo alloy wear-resistant coating, and the study would be divided into three stages: The initial stage is the study of the Ni-Mo alloy process by DC electrodeposition, and the use of the experimental designs to analyze how the main salt ratio, current density and pH value such process parameters affect on the coating properties, and tribological characteristics of coating. Secondly, the study of the Ni-Mo alloy process by pulse electrodeposition, and the use of the experimental designs to analyze how the pulse frequency and duty cycle such process parameters affect on the coating properties, and tribological characteristics of coating. Third, the study of the DC and pulse electrodeposited Ni-Mo alloy heat treatment with optimal parameters, and the use of experimental design to analyze the temperature and time of heat treatment affect on the coating and tribological characteristics of the coating. In the first stage of the experimental results, the DC electrodeposited Ni-Mo alloy process in the high main salt, high pH and low current density will make the coating having the highest current efficiency and would be more meticulous, smooth. The best parameters in the nickel-molybdenum are as below：the main salt ratio is as 30:1, the pH value is as 9.5 and the current density is as 2(ASD), molybdenum content of the coating is 11.56(wt.%), the hardness of the coating is up to 618(HV), the coating weight is 1.304(g), and the average wear weight loss is as 2.4×10-3(mg/m). In the second stage of the experimental results, the pulse electrodeposited Ni-Mo alloy process in the low frequency will make the hardness, thickness and roughness of the coating having the best performance. Duty cycle is positively correlated with the thickness of the coating. However, in the high Duty cycle, the wear scars will have a lot of adhesion phenomena. The best parameters in the nickel-molybdenum are as below：the Duty cycle is as 0.3, frequency is of 10(Hz), molybdenum content of the coating is 17.40(wt.%), the hardness of the coating is up to 711(HV), the coating weight is 0.914(g), and the average wear weight loss is as 3.6×10-3(mg /m). The third stage of experimental results show that DC electrodeposition in 500(℃), 1 hour heat treatment has the best performance, the hardness is up to 840(HV) and the average wear weight loss as 1.4×10-3(mg/m). The pulsed electrodeposition in 500(℃), 5 hours heat treatment has the best performance, the hardness is up to 895(HV) and the average wear weight loss is as 1.0×10-3(mg/m). The wear lose is only 28 % of the wear loss without heat treatment. The pulse electrodeposition heat treatment is superior to DC electrodeposition heat treatment, probably because the molybdenum content of the pulse electrodeposition coating is higher than the DC eletrodeposition, resulting in the process to strengthen and having better heat resistance. Before the heat treatment, the DC electrodeposition's the current efficiency and average wear weight loss are better than the pulse electrodeposition, but the hardness and the molybdenum content of the coating is more poor. After the heat treatment, probably because of the high molybdenum content of the pulse electrodeposition coating, the hardness, the average wear weight loss and heat resistance is superior than the DC electrodeposition. For the Ni-Mo surface coating process development and tribology research, this study made a specific assessment and would help the Department of Defense to have the applications of the Ni-Mo alloy's wear resistance for extending the life in weapons, equipments and systems. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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