本文關(guān)鍵詞： 超高強度不銹鋼 固溶 時效 析出相 氫脆敏感性　出處：《蘭州理工大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

【摘要】：作為超高強度不銹鋼的重要組成部分,馬氏體沉淀硬化不銹鋼因其優(yōu)良的強韌性匹配、良好的耐蝕性,作為重要的工程結(jié)構(gòu)用鋼,在航空航天、海洋工程及能源等重大領(lǐng)域得到了廣泛的應(yīng)用。鑒于該鋼種合金元素體系較為復(fù)雜,經(jīng)過熱處理后鋼中的析出相種類較多,且隨著強度的進一步提升,導(dǎo)致鋼對氫脆的敏感性進一步提高,這些因素極大的制約了材料的進一步發(fā)展和應(yīng)用。故此,針對熱處理對1900MPa級別USS122超高強度不銹鋼的強韌化機理和氫脆敏感性影響的研究,具有十分重要的理論意義和指導(dǎo)實際應(yīng)用的價值。本文應(yīng)用光學(xué)顯微鏡(Optical Microscopy)、掃描電子顯微鏡(Scanning Electron Microscopy)、透射電子顯微鏡(Transmission Electron Microscopy)、電子背散射衍射(EBSD Electron Back-scattered Diffraction)、Thermal-calc熱力學(xué)計算等實驗方法,分析和觀察了不同熱處理工藝下USS122鋼的微觀組織。實驗結(jié)果表明,1080℃固溶處理后,鋼中原始晶粒上分布的大量粗大M6C碳化物、χ相基本全溶,此時鋼的綜合力學(xué)性能最佳;固溶溫度較低時(如1000℃),則第二相未全溶,影響了鋼的韌性;固溶溫度過高(如1100℃),則鋼的組織顯著粗大化,導(dǎo)致屈服強度下降。經(jīng)1080℃固溶處理保溫1h后油淬、-73℃深冷處理8h、540℃時效保溫4h空冷(峰時效)后鋼的綜合力學(xué)性能最優(yōu),抗拉強度Rm≥1900MPa,沖擊吸收功值達45J。此時,鋼中析出了大量細小彌散的Laves相,尺寸在5~11nm左右,產(chǎn)生了強烈的沉淀硬化效應(yīng),極大地提高了鋼的強度。時效溫度較低或保溫時間較短(欠時效)時,鋼中析出量相較少;而過時效階段時,鋼中析出相變得粗大,降低了鋼的強度。此外,鋼中基體間隙處薄膜狀逆轉(zhuǎn)變奧氏體的形成對于鋼韌性的提高具有重要意義。通過慢速應(yīng)變拉伸實驗和TDS氫熱分析實驗對鋼充氫前后的缺口抗拉強度及全氫含量進行了測定。結(jié)果表明,充氫后鋼中發(fā)生了氫脆現(xiàn)象,斷口根部呈典型的沿晶斷裂形貌,缺口抗拉強度有較大幅度下降,且鋼的氫脆敏感性隨時效溫度的上升呈先上升后下降的趨勢,與時效溫度對鋼的強度的影響規(guī)律相近;時效溫度在520~560℃時氫脆敏感性最高。
[Abstract]:As an important part of ultra-high strength stainless steel, martensite precipitated hardened stainless steel, due to its excellent strength and toughness matching, good corrosion resistance, as an important engineering structure steel, in aerospace, In view of the complexity of the alloying element system, there are many kinds of precipitated phases in the steel after heat treatment, and with the further increase of the strength, the steel is widely used in many fields, such as ocean engineering and energy. As a result, the sensitivity of steel to hydrogen embrittlement is further improved, which greatly restricts the further development and application of materials. Therefore, the effect of heat treatment on the strengthening and toughening mechanism and hydrogen embrittlement sensitivity of 1900 MPA USS122 ultra high strength stainless steel is studied. In this paper, optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM), transmission electron microscope (TEM), transmission Electron microscopy( TEM) and EBSD Electron Back-scattered diffusion (EBSD) are used to calculate Thermal-calc thermodynamics. The microstructure of USS122 steel under different heat treatment conditions was analyzed and observed. The experimental results showed that after solution treatment at 1080 鈩，

本文編號：1508012