1. 動電位(wei)極化曲線分析

  2507雙相不銹鋼經1000℃、1050℃、1100℃、1150℃及1200℃固溶處理后于30℃在3.5%NaCl溶液中的動電位極化曲線如圖5.3所示。從圖5.3可知各固溶溫度下2507雙相不銹鋼(gang)的極化曲線形狀大體相同，都具有明顯的鈍化區域，且鈍化區域都較寬。國標GB 4334.9-1984規定陽極極化曲線上與電流密度值為100μA/c㎡相應的電位為擊破電位（Eb),擊破電位指金屬材料最先產生點腐蝕的電位，其值越高表明材料產生孔蝕的傾向越低。當2507雙相不銹鋼主要化學成分一定時，其表面保護膜的均勻性及穩定性跟鋼的兩相組織（α相及γ相）有著密切聯系，鋼中的α相和γ相分布均勻、相比例接近1:1時保護膜比較穩定且對鋼的點蝕行為有較好的阻礙作用；當鋼中的α相和γ相分布不均勻時易導致鋼表面保護膜遭受破壞，降低鋼的抗點蝕性能。經過不同固溶溫度處理的DSS2507的擊破電位（Eb)值如表5.1所列。從表5.1可知DSS2507于3.5%NaCl溶液中的擊破電位（Eb)隨著固溶熱處理溫度的上升呈現先變大后減小的走勢，1050℃時點蝕電位值最高，表明該固溶溫度下2507雙相鋼發生點蝕的傾向較低。固溶溫度為1000℃時2507雙相不銹鋼中鐵素體相跟奧氏體相界處有σ相析出，其附近較易形成貧鉻及貧鉬區域，造成該固溶熱處理溫度下鋼的抗點腐蝕能力較弱；1050℃時DSS2507中的兩相結構（鐵素體α相及奧氏體y相）分布較均勻，相比例約為1:1,有利于鋼表面鈍化膜的穩定，進而對點蝕具有較好的抑制作用，表現為點蝕電位Eb值較高；然而隨固溶熱處理溫度繼續上升，鐵素體α相量增多奧氏體γ相量減少，導致鐵素體形成元素Cr和Mo的濃度減小，而奧氏體形成元素N濃度升高，因此Cr、Mo和N在這兩種組織結構中的分布變得不均勻，由于Cr、Mo和N是鋼的主要耐點蝕元素，因此鋼的耐腐蝕能力降低。具體表現為點蝕電位E,值降低，所以在1050~1200℃溫度范圍內2507雙相不銹鋼的點蝕電位降低。此外從表5.1中列出的（Eb-Ecom)值可以看出其值變化趨勢跟點蝕電位（Eb)值的變化趨勢相同，都呈先升高后降低的趨勢。由于（Eb-Ecom)差值表示形核阻力的大小，因此由（Eb-Ecom)差值變化趨勢可知點蝕形核的阻力也是先增大后減小，即隨著固溶溫度的升高鋼的抗點蝕性能呈先增強后減弱的趨勢。此外從表5.1中可以看出，隨固溶熱處理溫度的上升自腐蝕電流密度（Icorr)先降低后增高，1050℃時自腐蝕電流密度較低為3.5367×10-7A/c㎡.綜上所述，固溶處理溫度為1050℃時2507雙相不銹鋼有較好的抗腐蝕能力。

  固溶態為1050℃的(de)(de)(de)(de)(de)(de)2507雙相(xiang)(xiang)(xiang)不銹鋼于(yu)3.5%NaCl溶液(ye)中(zhong)動電位極化(hua)后(hou)的(de)(de)(de)(de)(de)(de)腐蝕(shi)(shi)形(xing)貌如(ru)圖5.4所示，圖中(zhong)深(shen)色是(shi)鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)(xiang)、淺(qian)色是(shi)奧(ao)(ao)氏(shi)體(ti)(ti)y相(xiang)(xiang)(xiang)、黑色圓點(dian)(dian)是(shi)點(dian)(dian)蝕(shi)(shi)坑(keng)。從圖5.4可知點(dian)(dian)蝕(shi)(shi)坑(keng)主要存在于(yu)鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)x相(xiang)(xiang)(xiang)上(shang)，這說明奧(ao)(ao)氏(shi)體(ti)(ti)y相(xiang)(xiang)(xiang)比(bi)(bi)鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)(xiang)要穩定(ding)，有著較(jiao)優的(de)(de)(de)(de)(de)(de)抗(kang)(kang)點(dian)(dian)腐蝕(shi)(shi)性能。奧(ao)(ao)氏(shi)體(ti)(ti)γ相(xiang)(xiang)(xiang)相(xiang)(xiang)(xiang)比(bi)(bi)于(yu)鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)(xiang)有較(jiao)好的(de)(de)(de)(de)(de)(de)抗(kang)(kang)點(dian)(dian)蝕(shi)(shi)性能的(de)(de)(de)(de)(de)(de)原因在于(yu)元(yuan)素(su)(su)(su)(su)N的(de)(de)(de)(de)(de)(de)作(zuo)用。元(yuan)素(su)(su)(su)(su)N是(shi)奧(ao)(ao)氏(shi)體(ti)(ti)形(xing)成元(yuan)素(su)(su)(su)(su)，于(yu)奧(ao)(ao)氏(shi)體(ti)(ti)γ相(xiang)(xiang)(xiang)中(zhong)的(de)(de)(de)(de)(de)(de)溶解度要比(bi)(bi)在鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)(xiang)中(zhong)的(de)(de)(de)(de)(de)(de)大，此外N能夠讓(rang)Cr和(he)Mo元(yuan)素(su)(su)(su)(su)從鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)(xiang)遷移到(dao)奧(ao)(ao)氏(shi)體(ti)(ti)γ相(xiang)(xiang)(xiang)中(zhong)，N顯著影(ying)響著這兩(liang)(liang)種(zhong)元(yuan)素(su)(su)(su)(su)在奧(ao)(ao)氏(shi)體(ti)(ti)γ相(xiang)(xiang)(xiang)和(he)鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)(xiang)中(zhong)的(de)(de)(de)(de)(de)(de)分配，兩(liang)(liang)相(xiang)(xiang)(xiang)中(zhong)合金(jin)元(yuan)素(su)(su)(su)(su)含(han)量的(de)(de)(de)(de)(de)(de)差值隨N元(yuan)素(su)(su)(su)(su)含(han)量的(de)(de)(de)(de)(de)(de)增多而(er)降低(di)，所以(yi)奧(ao)(ao)氏(shi)體(ti)(ti)γ相(xiang)(xiang)(xiang)的(de)(de)(de)(de)(de)(de)點(dian)(dian)蝕(shi)(shi)電位較(jiao)鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)(xiang)要高(gao)，從而(er)蝕(shi)(shi)坑(keng)較(jiao)先在Eb相(xiang)(xiang)(xiang)對(dui)比(bi)(bi)較(jiao)低(di)的(de)(de)(de)(de)(de)(de)鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)(xiang)中(zhong)產(chan)生。

2. 交流(liu)阻(zu)抗(kang)測試分析

  1000℃、1050℃、1100℃、1150℃及(ji)1200℃固(gu)溶(rong)(rong)態的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)2507 雙(shuang)(shuang)相(xiang)(xiang)不(bu)(bu)銹(xiu)鋼(gang)(gang)30℃下(xia)于(yu)3.5%NaCl溶(rong)(rong)液(ye)(ye)中的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)Nyquist 圖如圖5.5所示(shi)，從圖中可以(yi)很明顯看出(chu)隨固(gu)溶(rong)(rong)熱(re)處(chu)理(li)溫度(du)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)增(zeng)高(gao)(gao)(gao)(gao)容(rong)(rong)抗(kang)(kang)(kang)弧(hu)(hu)(hu)半徑(jing)(jing)先增(zeng)大(da)(da)后(hou)(hou)(hou)減小(xiao)(xiao)，1050℃時容(rong)(rong)抗(kang)(kang)(kang)弧(hu)(hu)(hu)半徑(jing)(jing)最大(da)(da)。通常情(qing)況下(xia)界面(mian)(mian)間電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)遷移(yi)(yi)(yi)促進了高(gao)(gao)(gao)(gao)頻區容(rong)(rong)抗(kang)(kang)(kang)弧(hu)(hu)(hu)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)形成(cheng)，容(rong)(rong)抗(kang)(kang)(kang)弧(hu)(hu)(hu)與雙(shuang)(shuang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)層(ceng)容(rong)(rong)抗(kang)(kang)(kang)及(ji)金(jin)屬材料溶(rong)(rong)解的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)綜合作(zuo)用(yong)有(you)(you)關，并且(qie)(qie)金(jin)屬－溶(rong)(rong)液(ye)(ye)界面(mian)(mian)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)轉移(yi)(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)影響著容(rong)(rong)抗(kang)(kang)(kang)弧(hu)(hu)(hu)半徑(jing)(jing)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)大(da)(da)小(xiao)(xiao)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)在(zai)金(jin)屬－溶(rong)(rong)液(ye)(ye)界面(mian)(mian)轉移(yi)(yi)(yi)時受到(dao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)阻(zu)(zu)(zu)(zu)力越(yue)強意味著容(rong)(rong)抗(kang)(kang)(kang)弧(hu)(hu)(hu)半徑(jing)(jing)越(yue)大(da)(da)，即意味著金(jin)屬的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)抗(kang)(kang)(kang)蝕(shi)性(xing)能(neng)(neng)越(yue)優(you)。從圖5.5容(rong)(rong)抗(kang)(kang)(kang)弧(hu)(hu)(hu)半徑(jing)(jing)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)改變趨勢可知(zhi)，固(gu)溶(rong)(rong)熱(re)處(chu)理(li)溫度(du)升(sheng)高(gao)(gao)(gao)(gao)使(shi)DSS2507的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)耐(nai)蝕(shi)性(xing)能(neng)(neng)首先增(zeng)強而后(hou)(hou)(hou)減弱(ruo)，1050℃時2507雙(shuang)(shuang)相(xiang)(xiang)不(bu)(bu)銹(xiu)鋼(gang)(gang)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)抗(kang)(kang)(kang)腐(fu)蝕(shi)性(xing)能(neng)(neng)最優(you)。不(bu)(bu)同固(gu)溶(rong)(rong)態的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)2507雙(shuang)(shuang)相(xiang)(xiang)不(bu)(bu)銹(xiu)鋼(gang)(gang)于(yu)3.5%NaCl溶(rong)(rong)液(ye)(ye)中的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)等(deng)效電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路如圖5.6所示(shi)，采用(yong)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)是R(C(R(CR))).Rs指參比電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)和工作(zuo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)間的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)溶(rong)(rong)液(ye)(ye)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)；Cd1為(wei)雙(shuang)(shuang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)層(ceng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)；Rct為(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)轉移(yi)(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)，其值(zhi)能(neng)(neng)夠反(fan)應(ying)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)在(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化(hua)(hua)(hua)學反(fan)應(ying)過程(cheng)中透過電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)以(yi)及(ji)于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)解質溶(rong)(rong)液(ye)(ye)中兩(liang)(liang)相(xiang)(xiang)界面(mian)(mian)遷移(yi)(yi)(yi)難易的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)大(da)(da)小(xiao)(xiao)，也能(neng)(neng)夠反(fan)映金(jin)屬發(fa)生腐(fu)蝕(shi)反(fan)應(ying)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)快慢，一般情(qing)況下(xia)Rct值(zhi)越(yue)高(gao)(gao)(gao)(gao)意味著電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)遷移(yi)(yi)(yi)過程(cheng)中所受的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)阻(zu)(zu)(zu)(zu)力越(yue)強，即材料的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)耐(nai)腐(fu)蝕(shi)性(xing)能(neng)(neng)越(yue)好(hao)；Cf表(biao)示(shi)鈍(dun)化(hua)(hua)(hua)膜(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)，Rf表(biao)示(shi)鈍(dun)化(hua)(hua)(hua)膜(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)。采用(yong)ZsimpWin軟(ruan)件(jian)對等(deng)效電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路模擬計算得到(dao)各元件(jian)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)數值(zhi)如表(biao)5.2所列。從表(biao)中看出(chu)雙(shuang)(shuang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)層(ceng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)（Cdl)及(ji)鈍(dun)化(hua)(hua)(hua)膜(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)（Cr)隨固(gu)溶(rong)(rong)溫度(du)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)升(sheng)高(gao)(gao)(gao)(gao)呈先減小(xiao)(xiao)后(hou)(hou)(hou)增(zeng)大(da)(da)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)趨勢；電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)轉移(yi)(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)（Rct)和鈍(dun)化(hua)(hua)(hua)膜(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)（Rf)呈先變大(da)(da)后(hou)(hou)(hou)減小(xiao)(xiao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)趨勢，即電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化(hua)(hua)(hua)學反(fan)應(ying)阻(zu)(zu)(zu)(zu)力隨固(gu)溶(rong)(rong)熱(re)處(chu)理(li)溫度(du)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)增(zeng)高(gao)(gao)(gao)(gao)先增(zeng)強后(hou)(hou)(hou)減弱(ruo)，2507雙(shuang)(shuang)相(xiang)(xiang)不(bu)(bu)銹(xiu)鋼(gang)(gang)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)抗(kang)(kang)(kang)腐(fu)蝕(shi)性(xing)能(neng)(neng)表(biao)現(xian)(xian)為(wei)先增(zeng)強后(hou)(hou)(hou)減弱(ruo)。1000℃時鋼(gang)(gang)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)相(xiang)(xiang)界處(chu)有(you)(you)σ相(xiang)(xiang)析(xi)出(chu)，σ相(xiang)(xiang)硬(ying)而脆(cui)降(jiang)(jiang)低了鋼(gang)(gang)表(biao)面(mian)(mian)鈍(dun)化(hua)(hua)(hua)膜(mo)(mo)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)穩定(ding)，表(biao)現(xian)(xian)為(wei)具有(you)(you)較低的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)鈍(dun)化(hua)(hua)(hua)膜(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)（Rf);1050℃時鋼(gang)(gang)中的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)兩(liang)(liang)相(xiang)(xiang)比例約為(wei)1:1,兩(liang)(liang)相(xiang)(xiang)分(fen)布較均勻且(qie)(qie)成(cheng)分(fen)穩定(ding)有(you)(you)利(li)于(yu)鈍(dun)化(hua)(hua)(hua)膜(mo)(mo)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)穩定(ding)，具體表(biao)現(xian)(xian)為(wei)鈍(dun)化(hua)(hua)(hua)膜(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)（Rf)值(zhi)較高(gao)(gao)(gao)(gao)，表(biao)明此刻(ke)離子(zi)遷移(yi)(yi)(yi)時所受阻(zu)(zu)(zu)(zu)力較大(da)(da)，進而2507雙(shuang)(shuang)相(xiang)(xiang)不(bu)(bu)銹(xiu)鋼(gang)(gang)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)抗(kang)(kang)(kang)腐(fu)蝕(shi)能(neng)(neng)力最佳；固(gu)溶(rong)(rong)熱(re)處(chu)理(li)溫度(du)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)進一步升(sheng)高(gao)(gao)(gao)(gao)使(shi)鋼(gang)(gang)中的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)兩(liang)(liang)相(xiang)(xiang)比例失調，表(biao)現(xian)(xian)為(wei)鐵素體相(xiang)(xiang)含量大(da)(da)幅升(sheng)高(gao)(gao)(gao)(gao)，奧(ao)氏體相(xiang)(xiang)含量減小(xiao)(xiao)，不(bu)(bu)利(li)于(yu)鋼(gang)(gang)表(biao)面(mian)(mian)鈍(dun)化(hua)(hua)(hua)膜(mo)(mo)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)穩定(ding)，導(dao)致鈍(dun)化(hua)(hua)(hua)膜(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)（Rf)減小(xiao)(xiao)，實際表(biao)現(xian)(xian)為(wei)鋼(gang)(gang)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)抗(kang)(kang)(kang)蝕(shi)性(xing)能(neng)(neng)下(xia)降(jiang)(jiang)，這(zhe)與動電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位掃描獲得的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)結論(lun)相(xiang)(xiang)同。