【摘要】：18Ni300馬氏體時(shí)效鋼以其優(yōu)異的強(qiáng)韌匹配性,在航空、航天和核電等重要領(lǐng)域得到廣泛應(yīng)用�，F(xiàn)有研究表明表面氮化后18Ni馬氏體時(shí)效鋼的疲勞抗力和磨損抗力明顯提高,這進(jìn)一步拓寬了 18Ni馬氏體時(shí)效鋼的使用范疇。然而,氮化后表面高硬度氮化層對(duì)材料強(qiáng)韌性的影響缺乏系統(tǒng)性的研究。本文通過(guò)研究18Ni300馬氏體時(shí)效鋼的熱處理工藝,以及離子氮化和氣體氮化對(duì)其力學(xué)性能的影響,得到適合18Ni300馬氏體時(shí)效鋼的氮化工藝。研究結(jié)果表明在820℃×1小時(shí)的固溶處理前,進(jìn)行900℃×1小時(shí)的預(yù)處理,可以顯著細(xì)化18Ni300馬氏體時(shí)效鋼晶粒。在480℃時(shí)效6-12小時(shí),強(qiáng)韌度匹配最佳。提高時(shí)效溫度,會(huì)縮短最佳強(qiáng)韌度所需時(shí)效時(shí)間。同時(shí),時(shí)效溫度和時(shí)間會(huì)對(duì)18Ni300馬氏體時(shí)效鋼的缺口敏感性有一定影響。對(duì) 480℃×24h、480℃×48h,500℃×24h,500℃×48h 四種不同的氮化制度進(jìn)行研究,得到不同氮化制度對(duì)氮化層表面硬度、氮化層深和硬度分布對(duì)材料性能的影響。升高氮化溫度和延長(zhǎng)氮化時(shí)間對(duì)氮化層硬度影響不大,但是會(huì)提高含氮化層構(gòu)件的缺口敏感性,缺口敏感指數(shù)由480℃×24h的1.18,降低到500℃×48h的0.917。極低位移速度(0.0015mm/min)缺口拉伸的抗拉強(qiáng)度不下降,證明氣體氮化并未增大延遲斷裂傾向。480℃×6小時(shí)時(shí)效后,再進(jìn)行480℃×9小時(shí)的離子氮化,材料表面形成102μm的氮化層,其硬度從表面HV820平緩下降到基體的HV610。氮化層表面形成Fe4N硬化相,未出現(xiàn)Fe2.3N脆性相。與氣體氮化相比,離子氮化工藝復(fù)雜,不適合大型構(gòu)件。適合18Ni300馬氏體時(shí)效鋼的最佳氮化工藝為480℃氣體氮化48小時(shí)。
[Abstract]:18Ni300 maraging steel is widely used in aviation, aerospace and nuclear power due to its excellent strength and toughness matching. The present research shows that the fatigue resistance and wear resistance of 18Ni maraging steel after surface nitridation are obviously improved, which further widens the scope of application of 18Ni maraging steel. However, there is no systematic study on the effect of high hardness nitrided layer on the strength and toughness of the materials after nitridation. By studying the heat treatment process of 18Ni300 maraging steel and the effects of ion nitridation and gas nitriding on its mechanical properties, a suitable nitriding process for 18Ni300 maraging steel was obtained. The results show that the grain size of 18Ni300 maraging steel can be significantly refined by pretreatment at 900 鈩，

【學(xué)位級(jí)別】：碩士


本文編號(hào)：2399776