本實驗主要在於研究無電鍍鎳對S45C中碳鋼機械性質的影響,藉由無電鍍鎳析鍍於中碳鋼表面來改善其硬度及耐磨耗性。酸浴及鹼浴所析鍍之試片進行不同溫度的熱處理,熱處理與未熱處理之試片分別進行不同荷重的硬度測試,因鍍層厚度較薄,故測試時使用維氏硬度計讓基材的影響降至最低。從酸浴及鹼浴中各選出一最高硬度來進行磨耗與衝擊試驗,並與基材進行比較。 實驗結果得知,酸浴及鹼浴為pH5及pH8時具有最高硬度,於荷重50克時其最高硬度值分別為HV0.05 701及HV0.05 803﹔熱處理後pH5及pH8於350°C及300°C出現最高硬度,於荷重50克時最高硬度值分別為HV0.05 1027與HV0.05 1066。熱處理後pH5及pH8的衝擊值分別為27.9與19.2 Joule,與基材的7.55 Joule比較下高出許多,經斷面的觀察推測應是熱處理時造成基材軟化所致,與鍍層較無直接關係。磨耗測試皆以熱處理後的為最佳,因熱處理時產生析出硬化使其硬度提高,故硬度提高也使磨耗量減少,耐磨耗性增加。 為了使硬度與耐磨耗性再次增加,故於pH5及pH8無電鍍浴中添加氧化鋁(Al2O3)陶瓷粉末,使其形成鎳磷-氧化鋁複合鍍層,並分別經由350°C及300°C熱處理後,測定其硬度與耐磨耗性,由實驗結果及數據分析得知,pH5及pH8初析鍍層與熱處理後試片的硬度皆有明顯提升,耐磨耗性也因添加氧化鋁陶瓷粉末而增加。
This research is to study the effect of mechanical properties on mild carbon steel (S45C) by electroless nickel plating. Meanwhile, to improve the surface hardness and wear resistance of S45C steels. The plating specimens used acid and alkaline baths which were heat treated by different temperature. Both of the heat treatment and un-treated specimens used different loading of the hardness test. Because the thickness of coating was lower, so we used micro-vickers hardness tester to minimize the influence of substrate. Beside, we select a maximum hardness of acid and alkaline baths which compared with the substrate through the wear and impact tests. The experiment results showed that the specimens used acid and alikline baths for pH5 and pH8 had the maximum hardness, the hardness values were the HV0.05 701 and HV0.05 803, respectively. Moreover, pH5 and pH8 of Ni-P coating on S45C steel after 350°C and 300°C heat treatment which will appear the highest hardness values, they were HV0.05 1027 and HV0.05 1066, respectively. After heat treatment, the impact energy of specimens of pH5 and pH8 were 27.9 and 19.2 joules, both of them were higher than the substrate (7.55 joule). By the observation of cross-section specimens, these results could be casused by softening substrate after heat treatment. In addition, due to the precipitation hardening increased the hardness of specimens after heat treatment. Therefore, the wear lost was decreased and wear resistance could be enhanced. All the specimens after heat treatment showed the best results of wear resistance. In order to increase the hardness and wear resistance of S45C steels, we add the alumina powder to the plating bath at pH5 and pH8, and then to produce a NiP-Al2O3 composite coating. The heat treatment temperature was similarly kept at 350°C and 300°C respectively, then to measure the properties of hardness and wear resistance. From the all test results and analysis data, the hardness of composite specimens was obviously increased for pH5 and pH8 via as-deposited and after heat treatment. The wear resistance was also obviously increased by added the Al2O3 powder.
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