鐵素體不銹鋼在高溫尿素環境中的腐蝕行為研究
2021-05-07 05:28:52
hualin
摘(zhai)要
對三種商(shang)用(yong)車(che)排氣(qi)系(xi)統用(yong)鐵(tie)素(su)(su)(su)體(ti)不(bu)(bu)(bu)(bu)銹(xiu)鋼(gang)(gang)（436L、439M、441）進行了(le)(le)(le)尿素(su)(su)(su)結(jie)晶腐(fu)蝕(shi)試驗，以模擬鐵(tie)素(su)(su)(su)體(ti)不(bu)(bu)(bu)(bu)銹(xiu)鋼(gang)(gang)在(zai)商(shang)用(yong)車(che)排氣(qi)系(xi)統內選擇(ze)性催(cui)化(hua)還原器(qi)（SCR）中的(de)(de)滲氮腐(fu)蝕(shi)行為。探(tan)究了(le)(le)(le)合(he)金成分(fen)及夾(jia)雜物對不(bu)(bu)(bu)(bu)銹(xiu)鋼(gang)(gang)耐高(gao)(gao)(gao)溫(wen)尿素(su)(su)(su)腐(fu)蝕(shi)的(de)(de)影響(xiang)，并依據EDS表征結(jie)果(guo)闡釋了(le)(le)(le)材料內部(bu)腐(fu)蝕(shi)的(de)(de)滲氮機(ji)理。研究表明，在(zai)高(gao)(gao)(gao)溫(wen)熱震疲(pi)勞和氧化(hua)的(de)(de)協(xie)同作(zuo)用(yong)下，高(gao)(gao)(gao)溫(wen)高(gao)(gao)(gao)氮的(de)(de)環(huan)境導致鐵(tie)素(su)(su)(su)體(ti)不(bu)(bu)(bu)(bu)銹(xiu)鋼(gang)(gang)晶界(jie)及晶內局部(bu)區(qu)域快速析(xi)(xi)出(chu)(chu)氮化(hua)鉻(ge)(ge)顆粒，造成晶界(jie)及基體(ti)局部(bu)區(qu)域貧(pin)鉻(ge)(ge)。由于(yu)436L和441不(bu)(bu)(bu)(bu)銹(xiu)鋼(gang)(gang)含有較高(gao)(gao)(gao)的(de)(de)Mo和Nb，其耐高(gao)(gao)(gao)溫(wen)尿素(su)(su)(su)腐(fu)蝕(shi)能力顯著(zhu)優于(yu)439M。此外，由于(yu)436L和441不(bu)(bu)(bu)(bu)銹(xiu)鋼(gang)(gang)中夾(jia)雜物細小彌散，也降低了(le)(le)(le)氮化(hua)鉻(ge)(ge)在(zai)夾(jia)雜物的(de)(de)形核析(xi)(xi)出(chu)(chu)幾(ji)率，成為提高(gao)(gao)(gao)抗高(gao)(gao)(gao)溫(wen)尿素(su)(su)(su)腐(fu)蝕(shi)的(de)(de)另(ling)一個因素(su)(su)(su)。
關鍵詞： 材料(liao)失效(xiao)與保護 ; 高溫尿素(su)腐蝕(shi) ; 晶間腐蝕(shi) ; X射線能譜(pu)分(fen)析(xi) ; 鐵素(su)體(ti)不銹鋼 ; 滲氮機(ji)理(li) ; 夾雜物
Abstract
In order to simulate the nitriding corrosion behavior of ferritic stainless steels in selective catalytic reduction （SCR） system of commercial vehicle, urea corrosion tests were carried out on three ferritic stainless steels （436L, 439M and 441） used in exhaust system of commercial vehicles. The influences of alloy composition and inclusions on high temperature urea corrosion resistance of ferritic stainless steels were investigated. The results show that under the synergistic effect of high temperature fatigue and oxidation, the high temperature and high nitrogen environment results in the rapid precipitation of chromium nitride particles at grain boundaris and in the local area of the ferritic stainless steels, resulting in chromium depletion. As 436L and 441 ferritic stainless steels contain higher Nb and Mo, thy present significantly higher resistance to high temperature urea corrosion rather than 439M. Moreover, due to the fine dispersion of inclusions in 436L and 441 stainless steels, the probability of nucleation and precipitation of chromium nitride on inclusions is also reduced, which is another cause for improving the resistance to high temperature urea corrosion of the relevant steels.
Keywords： materials failure and protection ; high temperature urea corrosion ; intergranular corrosion ; EDS ; ferritic stainless steels ; nitriding mechanism ; inclusion
