發(fā)布時(shí)間：2019-03-05 07:38

【摘要】：磨損、腐蝕和疲勞是機(jī)械零件或構(gòu)件失效的三種最主要的形式,表面改性處理技術(shù)是解決這一問(wèn)題的一種行之有效的手段。熱反應(yīng)擴(kuò)散法作為表面硬質(zhì)涂層制備方式的一種,具有成本較低,操作簡(jiǎn)單,滲層性能優(yōu)異的特點(diǎn)。鈦復(fù)合膜由于其優(yōu)異的物理化學(xué)性能被廣泛用于材料的表面強(qiáng)化改性以提高材料的顯微硬度、耐磨以及耐腐蝕性能。目前,采用熱反應(yīng)擴(kuò)散法制備鈦復(fù)合膜的工藝還不成熟,比如鹽浴的揮發(fā)性和氧化性問(wèn)題還有待解決。本文中,對(duì)鋼基體進(jìn)行預(yù)先滲碳和滲氮的處理以降低反應(yīng)溫度并縮短反應(yīng)時(shí)間來(lái)解決這一問(wèn)題。本文分別對(duì)20鋼預(yù)先滲碳以及45鋼預(yù)先滲氮后的試樣進(jìn)行鹽浴滲鈦處理,并對(duì)其顯微結(jié)構(gòu)和性能進(jìn)行了一定的研究。得到了以下幾點(diǎn)主要的結(jié)論:1.20鋼滲碳處理過(guò)程中析出了滲碳體并形成珠光體組織,共同構(gòu)成了近表面較厚的滲碳層;45鋼滲氮處理后表面形成了三層結(jié)構(gòu),從上至下依次為化合物層,擴(kuò)散層以及心部基體組織,其中表面化合物層主要的物相組成為ε-Fe2_3N和γ'-Fe4N。同時(shí),試樣外表面還形成了一層較薄的疏松層。2.Ti-Fe合金粉末比Ti02更適合作為鹽浴滲鈦的鈦源,綜合考慮鹽浴的揮發(fā)性,流動(dòng)性以及所制備滲層的質(zhì)量,在本實(shí)驗(yàn)條件下,900℃×3h是較為理想的鹽浴滲鈦處理工藝。3.滲碳20鋼經(jīng)900 ℃×3h滲鈦處理后,鋼基表面形成了致密的TiC滲層,滲層厚度值約為7.5 μm,滲層/基體間界面明顯,界面結(jié)合力的大小約為52 N,滲層的顯微硬度值約為1870±134HV;滲氮45鋼經(jīng)900 ℃ ×3 h滲鈦處理后,試樣表面形成了 TiCN滲層,滲層中含有Ti-Fe固溶體;滲層厚度值約為8.5 μm,滲層與基體間的界面呈鋸齒狀,界面結(jié)合力的大小為68 N,滲層的顯微硬度值約為 1685 ±112 HV。4.滲碳以及滲碳+滲鈦復(fù)合處理能夠有效提高20鋼基體的耐磨性。耐磨性的順序?yàn)?滲碳+滲鈦20鋼滲碳20鋼20鋼基體。摩擦磨損過(guò)程中三種試樣主要的磨損機(jī)制分別為:擦傷機(jī)制+氧化磨損、磨粒磨損、粘著磨損。滲氮處理能夠有效降低45鋼基體的摩擦系數(shù),但摩擦磨損過(guò)程中摩擦系數(shù)的變化較大;滲氮+滲鈦復(fù)合處理對(duì)45鋼基體的減磨性的影響較小,但摩擦磨損過(guò)程中摩擦系數(shù)的變化較小。耐磨性的順序?yàn)?滲氮+滲鈦45鋼45鋼基體滲氮45鋼。摩擦磨損過(guò)程中三種試樣主要的磨損機(jī)制分別為:氧化磨損、磨粒磨損、粘著磨損。相較而言,TiCN滲層比TiC滲層具有更加優(yōu)異的摩擦磨損性能。5.滲碳以及滲碳+滲鈦復(fù)合處理可以降低試樣的腐蝕速率提高其耐蝕性,耐腐蝕性順序?yàn)?滲碳20鋼滲碳+滲鈦20鋼20鋼基體;滲氮處理也可有效提高試樣的耐腐蝕性,但經(jīng)滲鈦復(fù)合處理后試樣的耐腐蝕性反而略微下降。相比TiC滲層,TiCN滲層自腐蝕電位更高,自腐蝕電流更小,具有更加優(yōu)異的耐腐蝕性能。
[Abstract]:Wear, corrosion and fatigue are the three main forms of failure of mechanical parts or components. Surface modification is an effective method to solve this problem. As one of the preparation methods of hard coating, the thermal reaction diffusion method has the advantages of low cost, simple operation and excellent properties of the coating. Because of its excellent physical and chemical properties, titanium composite films have been widely used in surface strengthening modification to improve the microhardness, wear resistance and corrosion resistance of the materials. At present, the process of preparing titanium composite film by thermal reaction diffusion method is not mature, such as the volatility and oxidation of salt bath still need to be solved. In this paper, the pre-carburizing and nitriding of the steel substrate is carried out to reduce the reaction temperature and shorten the reaction time to solve this problem. In this paper, pre-carburizing of 20 steel and pre-nitriding of 45 steel were treated by salt bath titanium, and their microstructure and properties were studied. The main conclusions are as follows: 1. Cementite was precipitated and pearlite was formed in the Carburizing process of steel 20, which together formed a thick cementite layer near the surface; The surface of 45 steel was nitrided into three layers: compound layer, diffusion layer and core matrix structure from top to bottom. The main phase composition of the surface compound layer was 蔚-Fe2_3N and 緯'- Fe4N.. At the same time, a thin loose layer was formed on the outer surface of the sample. 2.Ti-Fe alloy powder is more suitable for titanium source in salt bath than Ti02, considering the volatility and fluidity of salt bath and the quality of the prepared layer. Under the experimental conditions, 900 鈩，

本文編號(hào)：2434676