标题: | 离子氮化对铁-30 锰-9 铝-1.8 碳合金腐蚀及机械性质之影响 Corrosion and Mechanical Properties of Plasma Nitrided Fe-30 Mn-9 Al-1.8 C Alloy |
作者: | 孔睦颖 Koung, Mu-Ying 刘增丰 Liu, Tseng-Feng 材料科学与工程学系所 |
关键字: | 铁锰铝;离子氮化;腐蚀;机械性质;Fe-Mn-Al;plasma nitrided;corrosion;mechanical properties |
公开日期: | 2011 |
摘要: | 本篇论文的目的是藉由扫描式电子显微镜(SEM)来观察在铁-30 锰- 9铝- 1.8碳合金,经过1200℃、两小时固溶热处理(SHT)后淬火至室温再分别以450℃、12小时时效热处理或离子氮化处理;500℃、8小时时效热处理或离子氮化处理,其显微结构之变化,并且利用恒电位仪、X光绕射分析(XRD)、X光能量散射光谱仪(EDS)与微硬度试验机,探讨表面氮化处理过后其显微结构以及其对合金抗腐蚀性质和机械性质的影响。 在本实验中,未经过氮化处理之铁-30 锰- 9 铝- 1.8 碳合金,在电化学腐蚀测试后,并无明显之钝化区形成,但经氮化处理过后,可发现明显之钝化区生成。经由电子显微镜(SEM)以及X光绕射分析(XRD)进行观察,可发现经过离子氮化处理后之合金试片,其合金表面形成一层致密的氮化铝(AlN),使得合金在动态极化曲线中呈现稳定且宽广的钝化区与最低之腐蚀电流密度(ip),并且在以1% HCl溶液做为腐蚀液的浸蚀测试中,其每单位面积损失的重量有显着的下降。而以3.5% NaCl溶液极化测试后之试片,经由电子显微镜(SEM)观察其合金腐蚀状况,可发现未经氮化处理过之试片,从晶界大量向下腐蚀,而晶粒内的母相产生许多涡状腐蚀以及腐蚀的小孔洞,其腐蚀情况相当严重。而经过氮化处理后之试片其抗蚀能力大幅提升,经过极化测试过后,其在晶界开始造成腐蚀,而在晶粒内产生一些微小的孔洞,但其腐蚀情况相较于未氮化之试片有显着的改善,其晶界腐蚀的程度以及晶粒内腐蚀之规模大小有明显之差异。且试片经过氮化处理过后,其表面氮化层组成为AlN与少量之Fe4N,微硬度随氮化后深度变化之情形,氮化层的表面硬度最高为1800 Hv,而后往内部逐渐递减,相较于未氮化片有显着的表面强化效果。 The purpose of this study is to examine the microstructural development of the Fe-9 wt.%Al-30 wt.%Mn-1.8 wt.% C after being solution heat treat (SHT) quench to room temperature and then aging or plasma nitriding which processes were carried out at temperatures 450℃ for 12h and 500℃ for 8h by scanning electron microscopy(SEM). The corrosion resistance and mechanical properties of the alloy were also examined by electrochemical measurements, X-ray diffraction(XRD) and micro-hardness tester. In addition, the effects of microstructural development of plasma nitrided alloy on the corrosion resistance and mechanical properties were also investigated. In this study, it is clearly seen that no evidence of passivation region could be found in the Fe-30Mn-9Al-1.8C alloy without nitrided treatment after electrochemical corrosion test. After plasma nitrided, the passivation region of alloy could be obviously observed. The outmost surface of the nitride layers was a compact AlN layer after plasma nitrided. It is also seen in the potentiodynamic polarization curves that alloy possesses a stable and broad passivation region and a minimum corrosion current density(ip). The plasma nitrided sample had the lowest weight loss after immersion test in 1% HCl water solution. By SEM examination of the surface of corrosion tested, the untreated samples was heavily corroded from grain boundary and matrix of the samples became rough with large amount of pits after electrochemical corrosion test. In contrast, the corrosion surface of a nitrided sample was slightly corroded from grain boundary and corrosion was just occurred few little pits. The main phases of the nitride layer were AlN with few Fe4N. The hardness was decrease from surface 1800Hv rapidly to matrix about 550Hv near the nitride layer boundary after 500℃ plasma nirided for 8h. It is to say that plasma nitrided present significantly hardness enhance effect. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT079918567 http://hdl.handle.net/11536/49660 |
显示于类别: | Thesis |