1. 動電位極化(hua)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(xiang)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)2507雙相(xiang)(xiang)不銹鋼于(yu)(yu)3.5%NaCl溶液(ye)中(zhong)動電位(wei)極化后(hou)的(de)(de)腐(fu)蝕(shi)(shi)形(xing)貌如圖5.4所示，圖中(zhong)深色(se)是(shi)鐵(tie)(tie)(tie)素(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)、淺色(se)是(shi)奧(ao)(ao)氏(shi)(shi)體(ti)(ti)y相(xiang)(xiang)、黑色(se)圓點(dian)是(shi)點(dian)蝕(shi)(shi)坑。從(cong)(cong)圖5.4可知點(dian)蝕(shi)(shi)坑主(zhu)要(yao)存在(zai)于(yu)(yu)鐵(tie)(tie)(tie)素(su)(su)(su)體(ti)(ti)x相(xiang)(xiang)上(shang)，這說明(ming)奧(ao)(ao)氏(shi)(shi)體(ti)(ti)y相(xiang)(xiang)比鐵(tie)(tie)(tie)素(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)要(yao)穩(wen)定，有著(zhu)較(jiao)(jiao)(jiao)優(you)的(de)(de)抗點(dian)腐(fu)蝕(shi)(shi)性能。奧(ao)(ao)氏(shi)(shi)體(ti)(ti)γ相(xiang)(xiang)相(xiang)(xiang)比于(yu)(yu)鐵(tie)(tie)(tie)素(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)有較(jiao)(jiao)(jiao)好的(de)(de)抗點(dian)蝕(shi)(shi)性能的(de)(de)原因在(zai)于(yu)(yu)元(yuan)素(su)(su)(su)N的(de)(de)作用。元(yuan)素(su)(su)(su)N是(shi)奧(ao)(ao)氏(shi)(shi)體(ti)(ti)形(xing)成元(yuan)素(su)(su)(su)，于(yu)(yu)奧(ao)(ao)氏(shi)(shi)體(ti)(ti)γ相(xiang)(xiang)中(zhong)的(de)(de)溶解度要(yao)比在(zai)鐵(tie)(tie)(tie)素(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)中(zhong)的(de)(de)大，此外(wai)N能夠(gou)讓Cr和Mo元(yuan)素(su)(su)(su)從(cong)(cong)鐵(tie)(tie)(tie)素(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)遷移到奧(ao)(ao)氏(shi)(shi)體(ti)(ti)γ相(xiang)(xiang)中(zhong)，N顯著(zhu)影響著(zhu)這兩種(zhong)元(yuan)素(su)(su)(su)在(zai)奧(ao)(ao)氏(shi)(shi)體(ti)(ti)γ相(xiang)(xiang)和鐵(tie)(tie)(tie)素(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)中(zhong)的(de)(de)分(fen)配(pei)，兩相(xiang)(xiang)中(zhong)合(he)金元(yuan)素(su)(su)(su)含量的(de)(de)差值隨(sui)N元(yuan)素(su)(su)(su)含量的(de)(de)增(zeng)多而(er)降低(di)，所以(yi)奧(ao)(ao)氏(shi)(shi)體(ti)(ti)γ相(xiang)(xiang)的(de)(de)點(dian)蝕(shi)(shi)電位(wei)較(jiao)(jiao)(jiao)鐵(tie)(tie)(tie)素(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)要(yao)高，從(cong)(cong)而(er)蝕(shi)(shi)坑較(jiao)(jiao)(jiao)先在(zai)Eb相(xiang)(xiang)對比較(jiao)(jiao)(jiao)低(di)的(de)(de)鐵(tie)(tie)(tie)素(su)(su)(su)體(ti)(ti)α相(xiang)(xiang)中(zhong)產(chan)生。

2. 交流阻抗測試分析

  1000℃、1050℃、1100℃、1150℃及(ji)1200℃固(gu)溶(rong)(rong)態的(de)(de)(de)(de)(de)(de)(de)2507 雙(shuang)(shuang)相(xiang)(xiang)(xiang)不(bu)銹鋼(gang)30℃下(xia)于3.5%NaCl溶(rong)(rong)液(ye)中(zhong)(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)Nyquist 圖如圖5.5所(suo)示(shi)，從圖中(zhong)(zhong)(zhong)可(ke)以很明顯看出隨固(gu)溶(rong)(rong)熱處(chu)(chu)理(li)(li)溫度(du)(du)的(de)(de)(de)(de)(de)(de)(de)增(zeng)(zeng)(zeng)高(gao)(gao)(gao)(gao)容(rong)(rong)抗(kang)(kang)(kang)(kang)弧(hu)(hu)(hu)半(ban)(ban)徑(jing)先(xian)(xian)(xian)增(zeng)(zeng)(zeng)大(da)后減(jian)(jian)小(xiao)，1050℃時(shi)容(rong)(rong)抗(kang)(kang)(kang)(kang)弧(hu)(hu)(hu)半(ban)(ban)徑(jing)最(zui)大(da)。通常情(qing)況(kuang)下(xia)界(jie)(jie)面(mian)(mian)間電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)的(de)(de)(de)(de)(de)(de)(de)遷移(yi)(yi)促(cu)進(jin)(jin)了(le)高(gao)(gao)(gao)(gao)頻區容(rong)(rong)抗(kang)(kang)(kang)(kang)弧(hu)(hu)(hu)的(de)(de)(de)(de)(de)(de)(de)形(xing)成，容(rong)(rong)抗(kang)(kang)(kang)(kang)弧(hu)(hu)(hu)與雙(shuang)(shuang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)層(ceng)容(rong)(rong)抗(kang)(kang)(kang)(kang)及(ji)金(jin)(jin)屬(shu)材料溶(rong)(rong)解(jie)的(de)(de)(de)(de)(de)(de)(de)綜合作用有(you)關，并且(qie)金(jin)(jin)屬(shu)－溶(rong)(rong)液(ye)界(jie)(jie)面(mian)(mian)的(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)轉移(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)影(ying)響著容(rong)(rong)抗(kang)(kang)(kang)(kang)弧(hu)(hu)(hu)半(ban)(ban)徑(jing)的(de)(de)(de)(de)(de)(de)(de)大(da)小(xiao)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)在(zai)金(jin)(jin)屬(shu)－溶(rong)(rong)液(ye)界(jie)(jie)面(mian)(mian)轉移(yi)(yi)時(shi)受到(dao)的(de)(de)(de)(de)(de)(de)(de)阻(zu)力(li)越(yue)(yue)強(qiang)意(yi)味著容(rong)(rong)抗(kang)(kang)(kang)(kang)弧(hu)(hu)(hu)半(ban)(ban)徑(jing)越(yue)(yue)大(da)，即意(yi)味著金(jin)(jin)屬(shu)的(de)(de)(de)(de)(de)(de)(de)抗(kang)(kang)(kang)(kang)蝕(shi)(shi)性(xing)(xing)(xing)能(neng)越(yue)(yue)優。從圖5.5容(rong)(rong)抗(kang)(kang)(kang)(kang)弧(hu)(hu)(hu)半(ban)(ban)徑(jing)的(de)(de)(de)(de)(de)(de)(de)改變趨(qu)勢可(ke)知(zhi)，固(gu)溶(rong)(rong)熱處(chu)(chu)理(li)(li)溫度(du)(du)升高(gao)(gao)(gao)(gao)使DSS2507的(de)(de)(de)(de)(de)(de)(de)耐蝕(shi)(shi)性(xing)(xing)(xing)能(neng)首先(xian)(xian)(xian)增(zeng)(zeng)(zeng)強(qiang)而后減(jian)(jian)弱，1050℃時(shi)2507雙(shuang)(shuang)相(xiang)(xiang)(xiang)不(bu)銹鋼(gang)的(de)(de)(de)(de)(de)(de)(de)抗(kang)(kang)(kang)(kang)腐蝕(shi)(shi)性(xing)(xing)(xing)能(neng)最(zui)優。不(bu)同固(gu)溶(rong)(rong)態的(de)(de)(de)(de)(de)(de)(de)2507雙(shuang)(shuang)相(xiang)(xiang)(xiang)不(bu)銹鋼(gang)于3.5%NaCl溶(rong)(rong)液(ye)中(zhong)(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)等(deng)效電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路如圖5.6所(suo)示(shi)，采用的(de)(de)(de)(de)(de)(de)(de)是(shi)R(C(R(CR))).Rs指(zhi)參比電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)和(he)工作電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)間的(de)(de)(de)(de)(de)(de)(de)溶(rong)(rong)液(ye)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)；Cd1為(wei)(wei)雙(shuang)(shuang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)層(ceng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)；Rct為(wei)(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)轉移(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)，其(qi)值(zhi)能(neng)夠(gou)反(fan)(fan)應(ying)(ying)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)在(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化(hua)(hua)(hua)學反(fan)(fan)應(ying)(ying)過程中(zhong)(zhong)(zhong)透過電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)以及(ji)于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)質溶(rong)(rong)液(ye)中(zhong)(zhong)(zhong)兩(liang)相(xiang)(xiang)(xiang)界(jie)(jie)面(mian)(mian)遷移(yi)(yi)難易的(de)(de)(de)(de)(de)(de)(de)大(da)小(xiao)，也能(neng)夠(gou)反(fan)(fan)映(ying)金(jin)(jin)屬(shu)發生腐蝕(shi)(shi)反(fan)(fan)應(ying)(ying)的(de)(de)(de)(de)(de)(de)(de)快慢(man)，一般情(qing)況(kuang)下(xia)Rct值(zhi)越(yue)(yue)高(gao)(gao)(gao)(gao)意(yi)味著電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)遷移(yi)(yi)過程中(zhong)(zhong)(zhong)所(suo)受的(de)(de)(de)(de)(de)(de)(de)阻(zu)力(li)越(yue)(yue)強(qiang)，即材料的(de)(de)(de)(de)(de)(de)(de)耐腐蝕(shi)(shi)性(xing)(xing)(xing)能(neng)越(yue)(yue)好；Cf表(biao)(biao)示(shi)鈍化(hua)(hua)(hua)膜(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)，Rf表(biao)(biao)示(shi)鈍化(hua)(hua)(hua)膜(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)。采用ZsimpWin軟(ruan)件對(dui)等(deng)效電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路模擬計算得到(dao)各元件的(de)(de)(de)(de)(de)(de)(de)數值(zhi)如表(biao)(biao)5.2所(suo)列(lie)。從表(biao)(biao)中(zhong)(zhong)(zhong)看出雙(shuang)(shuang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)層(ceng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)（Cdl)及(ji)鈍化(hua)(hua)(hua)膜(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)（Cr)隨固(gu)溶(rong)(rong)溫度(du)(du)的(de)(de)(de)(de)(de)(de)(de)升高(gao)(gao)(gao)(gao)呈先(xian)(xian)(xian)減(jian)(jian)小(xiao)后增(zeng)(zeng)(zeng)大(da)的(de)(de)(de)(de)(de)(de)(de)趨(qu)勢；電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)轉移(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)（Rct)和(he)鈍化(hua)(hua)(hua)膜(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)（Rf)呈先(xian)(xian)(xian)變大(da)后減(jian)(jian)小(xiao)的(de)(de)(de)(de)(de)(de)(de)趨(qu)勢，即電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化(hua)(hua)(hua)學反(fan)(fan)應(ying)(ying)阻(zu)力(li)隨固(gu)溶(rong)(rong)熱處(chu)(chu)理(li)(li)溫度(du)(du)的(de)(de)(de)(de)(de)(de)(de)增(zeng)(zeng)(zeng)高(gao)(gao)(gao)(gao)先(xian)(xian)(xian)增(zeng)(zeng)(zeng)強(qiang)后減(jian)(jian)弱，2507雙(shuang)(shuang)相(xiang)(xiang)(xiang)不(bu)銹鋼(gang)的(de)(de)(de)(de)(de)(de)(de)抗(kang)(kang)(kang)(kang)腐蝕(shi)(shi)性(xing)(xing)(xing)能(neng)表(biao)(biao)現(xian)為(wei)(wei)先(xian)(xian)(xian)增(zeng)(zeng)(zeng)強(qiang)后減(jian)(jian)弱。1000℃時(shi)鋼(gang)的(de)(de)(de)(de)(de)(de)(de)相(xiang)(xiang)(xiang)界(jie)(jie)處(chu)(chu)有(you)σ相(xiang)(xiang)(xiang)析出，σ相(xiang)(xiang)(xiang)硬而脆(cui)降(jiang)低了(le)鋼(gang)表(biao)(biao)面(mian)(mian)鈍化(hua)(hua)(hua)膜(mo)的(de)(de)(de)(de)(de)(de)(de)穩(wen)(wen)(wen)定(ding)(ding)(ding)，表(biao)(biao)現(xian)為(wei)(wei)具有(you)較低的(de)(de)(de)(de)(de)(de)(de)鈍化(hua)(hua)(hua)膜(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)（Rf);1050℃時(shi)鋼(gang)中(zhong)(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)兩(liang)相(xiang)(xiang)(xiang)比例約為(wei)(wei)1:1,兩(liang)相(xiang)(xiang)(xiang)分布較均勻且(qie)成分穩(wen)(wen)(wen)定(ding)(ding)(ding)有(you)利于鈍化(hua)(hua)(hua)膜(mo)的(de)(de)(de)(de)(de)(de)(de)穩(wen)(wen)(wen)定(ding)(ding)(ding)，具體(ti)表(biao)(biao)現(xian)為(wei)(wei)鈍化(hua)(hua)(hua)膜(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)（Rf)值(zhi)較高(gao)(gao)(gao)(gao)，表(biao)(biao)明此刻離子遷移(yi)(yi)時(shi)所(suo)受阻(zu)力(li)較大(da)，進(jin)(jin)而2507雙(shuang)(shuang)相(xiang)(xiang)(xiang)不(bu)銹鋼(gang)的(de)(de)(de)(de)(de)(de)(de)抗(kang)(kang)(kang)(kang)腐蝕(shi)(shi)能(neng)力(li)最(zui)佳；固(gu)溶(rong)(rong)熱處(chu)(chu)理(li)(li)溫度(du)(du)的(de)(de)(de)(de)(de)(de)(de)進(jin)(jin)一步升高(gao)(gao)(gao)(gao)使鋼(gang)中(zhong)(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)兩(liang)相(xiang)(xiang)(xiang)比例失調，表(biao)(biao)現(xian)為(wei)(wei)鐵素(su)體(ti)相(xiang)(xiang)(xiang)含量(liang)大(da)幅升高(gao)(gao)(gao)(gao)，奧(ao)氏體(ti)相(xiang)(xiang)(xiang)含量(liang)減(jian)(jian)小(xiao)，不(bu)利于鋼(gang)表(biao)(biao)面(mian)(mian)鈍化(hua)(hua)(hua)膜(mo)的(de)(de)(de)(de)(de)(de)(de)穩(wen)(wen)(wen)定(ding)(ding)(ding)，導致鈍化(hua)(hua)(hua)膜(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)（Rf)減(jian)(jian)小(xiao)，實際表(biao)(biao)現(xian)為(wei)(wei)鋼(gang)的(de)(de)(de)(de)(de)(de)(de)抗(kang)(kang)(kang)(kang)蝕(shi)(shi)性(xing)(xing)(xing)能(neng)下(xia)降(jiang)，這與動電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位掃描獲(huo)得的(de)(de)(de)(de)(de)(de)(de)結論相(xiang)(xiang)(xiang)同。