1. 動(dong)電位極化曲線分(fen)析(xi)

  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(bu)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(xiu)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)(xiang)(xiang)(xiang)(xiang)(xiang)不銹鋼于3.5%NaCl溶液中(zhong)動(dong)電位(wei)極化后的(de)(de)腐蝕(shi)形貌如(ru)圖5.4所示，圖中(zhong)深色(se)是鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)、淺色(se)是奧(ao)(ao)(ao)氏(shi)(shi)體(ti)(ti)(ti)(ti)y相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)、黑色(se)圓(yuan)點(dian)是點(dian)蝕(shi)坑(keng)。從(cong)圖5.4可(ke)知點(dian)蝕(shi)坑(keng)主要(yao)存在(zai)于鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)(ti)(ti)x相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)上，這說明奧(ao)(ao)(ao)氏(shi)(shi)體(ti)(ti)(ti)(ti)y相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)比(bi)鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)要(yao)穩(wen)定，有(you)著較優的(de)(de)抗點(dian)腐蝕(shi)性能(neng)。奧(ao)(ao)(ao)氏(shi)(shi)體(ti)(ti)(ti)(ti)γ相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)比(bi)于鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)有(you)較好的(de)(de)抗點(dian)蝕(shi)性能(neng)的(de)(de)原因在(zai)于元(yuan)素(su)(su)(su)(su)N的(de)(de)作用。元(yuan)素(su)(su)(su)(su)N是奧(ao)(ao)(ao)氏(shi)(shi)體(ti)(ti)(ti)(ti)形成元(yuan)素(su)(su)(su)(su)，于奧(ao)(ao)(ao)氏(shi)(shi)體(ti)(ti)(ti)(ti)γ相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)中(zhong)的(de)(de)溶解度要(yao)比(bi)在(zai)鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)中(zhong)的(de)(de)大，此(ci)外N能(neng)夠讓Cr和Mo元(yuan)素(su)(su)(su)(su)從(cong)鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)遷移(yi)到奧(ao)(ao)(ao)氏(shi)(shi)體(ti)(ti)(ti)(ti)γ相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)中(zhong)，N顯著影響著這兩種元(yuan)素(su)(su)(su)(su)在(zai)奧(ao)(ao)(ao)氏(shi)(shi)體(ti)(ti)(ti)(ti)γ相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)和鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)中(zhong)的(de)(de)分(fen)配，兩相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)中(zhong)合(he)金元(yuan)素(su)(su)(su)(su)含量的(de)(de)差值隨N元(yuan)素(su)(su)(su)(su)含量的(de)(de)增多(duo)而降低，所以奧(ao)(ao)(ao)氏(shi)(shi)體(ti)(ti)(ti)(ti)γ相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)的(de)(de)點(dian)蝕(shi)電位(wei)較鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)要(yao)高，從(cong)而蝕(shi)坑(keng)較先在(zai)Eb相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)對比(bi)較低的(de)(de)鐵(tie)(tie)素(su)(su)(su)(su)體(ti)(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)中(zhong)產生。

2. 交流阻(zu)抗測(ce)試(shi)分析(xi)

  1000℃、1050℃、1100℃、1150℃及1200℃固(gu)(gu)(gu)溶(rong)(rong)態(tai)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)2507 雙(shuang)(shuang)相(xiang)(xiang)(xiang)不(bu)銹(xiu)鋼30℃下(xia)于(yu)3.5%NaCl溶(rong)(rong)液(ye)(ye)中(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)Nyquist 圖如(ru)圖5.5所(suo)(suo)示(shi)，從圖中(zhong)(zhong)可以很明顯看出隨固(gu)(gu)(gu)溶(rong)(rong)熱處(chu)理(li)溫(wen)(wen)度(du)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)增高(gao)(gao)容(rong)(rong)(rong)抗(kang)(kang)弧(hu)半(ban)徑(jing)先(xian)增大(da)(da)(da)后減(jian)小(xiao)，1050℃時容(rong)(rong)(rong)抗(kang)(kang)弧(hu)半(ban)徑(jing)最(zui)大(da)(da)(da)。通常情況下(xia)界面(mian)間(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)遷(qian)(qian)移(yi)(yi)促(cu)進了高(gao)(gao)頻區(qu)容(rong)(rong)(rong)抗(kang)(kang)弧(hu)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)形成，容(rong)(rong)(rong)抗(kang)(kang)弧(hu)與雙(shuang)(shuang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)層(ceng)容(rong)(rong)(rong)抗(kang)(kang)及金(jin)(jin)屬(shu)(shu)材料(liao)溶(rong)(rong)解(jie)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)綜合作用(yong)有(you)關，并(bing)且金(jin)(jin)屬(shu)(shu)－溶(rong)(rong)液(ye)(ye)界面(mian)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)轉移(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)影響(xiang)著容(rong)(rong)(rong)抗(kang)(kang)弧(hu)半(ban)徑(jing)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)大(da)(da)(da)小(xiao)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)在(zai)金(jin)(jin)屬(shu)(shu)－溶(rong)(rong)液(ye)(ye)界面(mian)轉移(yi)(yi)時受(shou)到的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)阻(zu)(zu)力越(yue)強意味(wei)著容(rong)(rong)(rong)抗(kang)(kang)弧(hu)半(ban)徑(jing)越(yue)大(da)(da)(da)，即(ji)意味(wei)著金(jin)(jin)屬(shu)(shu)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)抗(kang)(kang)蝕(shi)(shi)性(xing)能(neng)(neng)(neng)越(yue)優。從圖5.5容(rong)(rong)(rong)抗(kang)(kang)弧(hu)半(ban)徑(jing)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)改變趨(qu)(qu)勢(shi)可知，固(gu)(gu)(gu)溶(rong)(rong)熱處(chu)理(li)溫(wen)(wen)度(du)升(sheng)(sheng)高(gao)(gao)使(shi)DSS2507的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)耐蝕(shi)(shi)性(xing)能(neng)(neng)(neng)首先(xian)增強而后減(jian)弱，1050℃時2507雙(shuang)(shuang)相(xiang)(xiang)(xiang)不(bu)銹(xiu)鋼的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)抗(kang)(kang)腐(fu)(fu)蝕(shi)(shi)性(xing)能(neng)(neng)(neng)最(zui)優。不(bu)同(tong)固(gu)(gu)(gu)溶(rong)(rong)態(tai)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)2507雙(shuang)(shuang)相(xiang)(xiang)(xiang)不(bu)銹(xiu)鋼于(yu)3.5%NaCl溶(rong)(rong)液(ye)(ye)中(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)等(deng)效(xiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路如(ru)圖5.6所(suo)(suo)示(shi)，采用(yong)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)是(shi)R(C(R(CR))).Rs指參(can)比電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極和工(gong)作電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極間(jian)的(de)(de)(de)(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)阻(zu)(zu)；Cd1為(wei)(wei)(wei)(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)(rong)；Rct為(wei)(wei)(wei)(wei)(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)轉移(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)，其值(zhi)能(neng)(neng)(neng)夠反應(ying)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)在(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化學反應(ying)過(guo)程中(zhong)(zhong)透(tou)過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極以及于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)質溶(rong)(rong)液(ye)(ye)中(zhong)(zhong)兩相(xiang)(xiang)(xiang)界面(mian)遷(qian)(qian)移(yi)(yi)難易的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)大(da)(da)(da)小(xiao)，也能(neng)(neng)(neng)夠反映金(jin)(jin)屬(shu)(shu)發生腐(fu)(fu)蝕(shi)(shi)反應(ying)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)快慢，一般情況下(xia)Rct值(zhi)越(yue)高(gao)(gao)意味(wei)著電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)遷(qian)(qian)移(yi)(yi)過(guo)程中(zhong)(zhong)所(suo)(suo)受(shou)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)阻(zu)(zu)力越(yue)強，即(ji)材料(liao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)耐腐(fu)(fu)蝕(shi)(shi)性(xing)能(neng)(neng)(neng)越(yue)好；Cf表(biao)(biao)示(shi)鈍化膜(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)，Rf表(biao)(biao)示(shi)鈍化膜(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)。采用(yong)ZsimpWin軟件(jian)(jian)對等(deng)效(xiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路模擬計算得(de)到各(ge)元(yuan)件(jian)(jian)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)數值(zhi)如(ru)表(biao)(biao)5.2所(suo)(suo)列(lie)。從表(biao)(biao)中(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)(rong)（Cdl)及鈍化膜(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)（Cr)隨固(gu)(gu)(gu)溶(rong)(rong)溫(wen)(wen)度(du)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)升(sheng)(sheng)高(gao)(gao)呈先(xian)減(jian)小(xiao)后增大(da)(da)(da)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)趨(qu)(qu)勢(shi)；電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)轉移(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)（Rct)和鈍化膜(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)（Rf)呈先(xian)變大(da)(da)(da)后減(jian)小(xiao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)趨(qu)(qu)勢(shi)，即(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化學反應(ying)阻(zu)(zu)力隨固(gu)(gu)(gu)溶(rong)(rong)熱處(chu)理(li)溫(wen)(wen)度(du)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)增高(gao)(gao)先(xian)增強后減(jian)弱，2507雙(shuang)(shuang)相(xiang)(xiang)(xiang)不(bu)銹(xiu)鋼的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)抗(kang)(kang)腐(fu)(fu)蝕(shi)(shi)性(xing)能(neng)(neng)(neng)表(biao)(biao)現為(wei)(wei)(wei)(wei)(wei)先(xian)增強后減(jian)弱。1000℃時鋼的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)相(xiang)(xiang)(xiang)界處(chu)有(you)σ相(xiang)(xiang)(xiang)析出，σ相(xiang)(xiang)(xiang)硬而脆降低(di)了鋼表(biao)(biao)面(mian)鈍化膜(mo)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)穩定(ding)，表(biao)(biao)現為(wei)(wei)(wei)(wei)(wei)具(ju)有(you)較(jiao)(jiao)低(di)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)鈍化膜(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)（Rf);1050℃時鋼中(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)兩相(xiang)(xiang)(xiang)比例約為(wei)(wei)(wei)(wei)(wei)1:1,兩相(xiang)(xiang)(xiang)分布較(jiao)(jiao)均勻(yun)且成分穩定(ding)有(you)利于(yu)鈍化膜(mo)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)穩定(ding)，具(ju)體表(biao)(biao)現為(wei)(wei)(wei)(wei)(wei)鈍化膜(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)（Rf)值(zhi)較(jiao)(jiao)高(gao)(gao)，表(biao)(biao)明此(ci)刻離子遷(qian)(qian)移(yi)(yi)時所(suo)(suo)受(shou)阻(zu)(zu)力較(jiao)(jiao)大(da)(da)(da)，進而2507雙(shuang)(shuang)相(xiang)(xiang)(xiang)不(bu)銹(xiu)鋼的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)抗(kang)(kang)腐(fu)(fu)蝕(shi)(shi)能(neng)(neng)(neng)力最(zui)佳；固(gu)(gu)(gu)溶(rong)(rong)熱處(chu)理(li)溫(wen)(wen)度(du)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)進一步升(sheng)(sheng)高(gao)(gao)使(shi)鋼中(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)兩相(xiang)(xiang)(xiang)比例失調，表(biao)(biao)現為(wei)(wei)(wei)(wei)(wei)鐵素體相(xiang)(xiang)(xiang)含量大(da)(da)(da)幅(fu)升(sheng)(sheng)高(gao)(gao)，奧(ao)氏體相(xiang)(xiang)(xiang)含量減(jian)小(xiao)，不(bu)利于(yu)鋼表(biao)(biao)面(mian)鈍化膜(mo)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)穩定(ding)，導致鈍化膜(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)（Rf)減(jian)小(xiao)，實際表(biao)(biao)現為(wei)(wei)(wei)(wei)(wei)鋼的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)抗(kang)(kang)蝕(shi)(shi)性(xing)能(neng)(neng)(neng)下(xia)降，這與動電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)掃描獲得(de)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)結(jie)論相(xiang)(xiang)(xiang)同(tong)。