- 學位論文
氮氧化製程對SKD11工具鋼性質之研究
Effects of the Properties on SKD11 Tool Steel by Oxynitriding Processes
摘要
本研究利用JIS SKD11工具鋼並分為三種不同氮氧化處理參數，第一個階段改變氮氧化溫度(470°C-8 h、480°C-8 h、490°C-8 h及510°C-8 h)，並保持相同的後氧化時間(30 min)，以取得最佳的氮氧化溫度；第二個部分改變氮氧化持溫時間(480°C-6 h、480°C-8 h與480°C-10 h)，後氧化時間一樣保持30 min，最後改變後氧化時間(480°C-8 h-30 min、480°C-8 h-60 min與480°C-8 h-90 min)評估並比較氣體氮氧化製程參數對JIS SKD11機械性質及顯微結構之影響。 實驗結果顯示經磨耗試驗後氮氧化處理確實可提升表面硬度，經由XRD分析結果亦可得知JIS SKD11工具鋼經氮氧化後，試片表面均會形成一層ε相(Fe3N)組成之化合層，可提高材料表面之耐磨性。此外，提高氮氧化的溫度(470°C → 480°C → 490°C → 510°C)，保持相同的氮氧化時間(8 h)與後氧化時間(30 min)，可以發現隨著溫度越高，JIS SKD11會有滲氮層越深但硬度卻降低之趨勢，這和長時間高溫反應下，基材硬度軟化有關。 另一方面，在不同的氮氧化時間(480°C-6 h、480°C-8 h 與480°C-10 h)及後氧化30 min處理後，磨耗試驗結果顯示仍以8 h的氮氧化時間之耐磨性最佳。增加後氧化時間(480°C-8 h-30 min → 480°C-8 h-60 min → 480°C-8 h-90 min)結果發現增加氧化時間會影響氮氧化滲氮深度，滲氮深度從原來40 μm左右變成10 μm也導致硬度與磨耗性下降。綜合實驗結果顯示，利用480°C-8 h-30 min氮氧化製程對JIS SKD11工具鋼之性質最佳。
並列摘要
In this study, JIS SKD11 tool steel is used and divided into three parameters of oxynitriding treatment. The first step is to change the temperature of oxynitriding treatment (470°C-8 h, 480°C-8 h, 490°C-8 h and 510°C-8 h) and keep the same post-oxidation time (30 min), then to find the optimal temperature of nitriding. The second step is change the soaking time of oxynitriding treatment (480°C-6 h, 480°C-8 h and 480°C-10 h) and soaking time of post-oxidation is same. Finally, we use the different soaking time of post-oxidation (480°C-8 h-30 min, 480°C-8 h-60 min, and 480°C-8 h-90 min) to evaluate and compare the effects of mechanical properties and microstructure on JIS SKD11 steel by different parameters of oxynitriding treatment. The experimental result showed that the hardness was increased by oxynitriding treatment after wear test. By the XRD analysis, it showed the ε phase (Fe3N) compounds were appeared on the steel surface which increased the wear resistance of material. Beside, increased the temperature of oxynitriding (470°C → 480°C → 490°C → 510°C) and kept the same soaking time of oxynitriding and post-oxidation treatment. It can be found as the temperature is increasing, the thickness of nitriding layer is higher and hardness is lower for JIS SKD11 by oxynitriding treatment. This result show that the substrate begging to soften after longer time and higher temperature reaction. In addition, by the different oxynitriding time (480°C-6 h, 480°C-8 h and 480°C-10 h) and post-oxidation of 30 min, the optimal wear-resistance was appeared in 8 hours after west test. Increasing the soaking time of post-oxidation (480°C-8 h-30min → 480°C-8 h-60min → 480°C-8 h-90min), it will affect the depth of nitriding layer. In this study, the nitriding layer was from 40 μm decreased to 10 μm that result in the lower hardness and poor wear-resistance. All these experimental results show that the optimal parameters of oxynitriding is 480°C-8 h-30 min for JIS SKD11 tool steel.