本研究主要目的在探討高矽球墨鑄鐵在靜止空氣中之高溫氧化行為，觀察與分析氧化層的結構與成分，並說明不同添加合金(矽、鉬、釩、銅)及石墨球化率對高溫抗氧化的影響。實驗的進行是將試片放置於陶瓷坩堝內，在700與900 C空氣氣氛下之熱處理爐分別持溫4、20、50及96 h。實驗完成後量測其重量變化，並利用OM、SEM、EDS及EPMA觀察分析氧化層結構。
實驗結果顯示: (1)各球墨鑄鐵在700 C氧化後重量皆隨著時間的增加而增加，但是在900 C時球墨鑄鐵發生脫碳現象而使重量增加與時間的關係不明確，顯示球墨鑄鐵可以使用到700 C，但是卻不適合在更高的900 C空氣中使用；(2)在700及900 C氧化後，氧化層由外往內依序為Fe2O3、Fe3O4、Fe2SiO4+Fe3O4及SiO2。SiO2在合金與氧化層的介面處呈黑色薄膜，Fe2SiO4組織呈深灰色條紋或顆粒狀。由於矽擴散能力的限制，氧化層內層呈現為富矽的區域，而外層則為無矽的區域；(3)矽含量較高之球墨鑄鐵的抗氧化能力較佳，其與氧化過程是否會形成SiO2保護膜有密切關係；(4)高矽球墨鑄鐵的抗氧化能力雖然隨矽含量的增加而提升，但亦受添加合金元素的影響， Mo、V及Cu的添加會有助於抗氧化能力的提升，但在900 C時添加釩會造成負面的影響。

In this research it is aimed to investigate the oxidation behavior of high silicon ductile irons, and to identify the microstructure and chemistry of oxide layers. The effects of various alloying elements (Si、Mo、V、Cu) and graphite nodularity are also discussed in this study. Specimens set in crucibles were heated in a furnace at 700 and 900 C for 4、20、50 and 96 h, specimen weigh gains were measured after oxidation. The microstructure and chemistry of the oxide layers were examined by OM、SEM、EDS and EPMA.
The results show that: (1) For ductile irons, weight gains increase with increasing time after the oxidation at 700 C. Decarburization occurs at 900 C, which shows the relationship between weight gains and time was indefinite, indicating that ductile iron can be used up to 700 C, but below 900 C; (2) The order of oxide layers from outer to inner are Fe2O3、Fe3O4、Fe2SiO4+Fe3O4 and SiO2 respectively. The dark film lies in the alloy-oxide interface which is identified as SiO2, the grayish stringers and particles are Fe2SiO4. Since the restriction of Si diffusion rate, Si can only be found in the inner oxide, but only a trace of Si in the outer oxide; (3) The oxidation resistance of ductile iron increase with the increasing of Si content, which may relate to the formation of SiO2 film; (4)Although increasing Si promote the oxidation resistance, high Si ductile iron is also influenced by alloying elements, the addition of Mo、V and Cu enhance the oxidation resistance in the two investigated temperatures, but it is detrimental for adding V at 900 C.

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