1. 動電(dian)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(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(shuang)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(rong)態為(wei)1050℃的(de)(de)(de)2507雙相(xiang)(xiang)不銹鋼于3.5%NaCl溶(rong)液中(zhong)(zhong)動電位(wei)極化后的(de)(de)(de)腐蝕(shi)形貌如圖5.4所(suo)示，圖中(zhong)(zhong)深色是鐵(tie)(tie)(tie)素(su)體(ti)(ti)(ti)(ti)(ti)α相(xiang)(xiang)、淺(qian)色是奧(ao)(ao)氏(shi)(shi)(shi)體(ti)(ti)(ti)(ti)(ti)y相(xiang)(xiang)、黑色圓點(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)(tie)素(su)體(ti)(ti)(ti)(ti)(ti)x相(xiang)(xiang)上，這說明奧(ao)(ao)氏(shi)(shi)(shi)體(ti)(ti)(ti)(ti)(ti)y相(xiang)(xiang)比鐵(tie)(tie)(tie)素(su)體(ti)(ti)(ti)(ti)(ti)α相(xiang)(xiang)要(yao)穩定，有(you)(you)著較優的(de)(de)(de)抗點(dian)腐蝕(shi)性能。奧(ao)(ao)氏(shi)(shi)(shi)體(ti)(ti)(ti)(ti)(ti)γ相(xiang)(xiang)相(xiang)(xiang)比于鐵(tie)(tie)(tie)素(su)體(ti)(ti)(ti)(ti)(ti)α相(xiang)(xiang)有(you)(you)較好的(de)(de)(de)抗點(dian)蝕(shi)性能的(de)(de)(de)原因在(zai)于元(yuan)(yuan)素(su)N的(de)(de)(de)作用。元(yuan)(yuan)素(su)N是奧(ao)(ao)氏(shi)(shi)(shi)體(ti)(ti)(ti)(ti)(ti)形成(cheng)元(yuan)(yuan)素(su)，于奧(ao)(ao)氏(shi)(shi)(shi)體(ti)(ti)(ti)(ti)(ti)γ相(xiang)(xiang)中(zhong)(zhong)的(de)(de)(de)溶(rong)解度要(yao)比在(zai)鐵(tie)(tie)(tie)素(su)體(ti)(ti)(ti)(ti)(ti)α相(xiang)(xiang)中(zhong)(zhong)的(de)(de)(de)大，此外N能夠讓(rang)Cr和Mo元(yuan)(yuan)素(su)從(cong)鐵(tie)(tie)(tie)素(su)體(ti)(ti)(ti)(ti)(ti)α相(xiang)(xiang)遷移到奧(ao)(ao)氏(shi)(shi)(shi)體(ti)(ti)(ti)(ti)(ti)γ相(xiang)(xiang)中(zhong)(zhong)，N顯著影響著這兩(liang)種元(yuan)(yuan)素(su)在(zai)奧(ao)(ao)氏(shi)(shi)(shi)體(ti)(ti)(ti)(ti)(ti)γ相(xiang)(xiang)和鐵(tie)(tie)(tie)素(su)體(ti)(ti)(ti)(ti)(ti)α相(xiang)(xiang)中(zhong)(zhong)的(de)(de)(de)分配，兩(liang)相(xiang)(xiang)中(zhong)(zhong)合金元(yuan)(yuan)素(su)含量的(de)(de)(de)差值隨N元(yuan)(yuan)素(su)含量的(de)(de)(de)增多而(er)(er)降(jiang)低，所(suo)以奧(ao)(ao)氏(shi)(shi)(shi)體(ti)(ti)(ti)(ti)(ti)γ相(xiang)(xiang)的(de)(de)(de)點(dian)蝕(shi)電位(wei)較鐵(tie)(tie)(tie)素(su)體(ti)(ti)(ti)(ti)(ti)α相(xiang)(xiang)要(yao)高，從(cong)而(er)(er)蝕(shi)坑(keng)較先在(zai)Eb相(xiang)(xiang)對比較低的(de)(de)(de)鐵(tie)(tie)(tie)素(su)體(ti)(ti)(ti)(ti)(ti)α相(xiang)(xiang)中(zhong)(zhong)產生(sheng)。

2. 交流阻抗測試分析

  1000℃、1050℃、1100℃、1150℃及(ji)1200℃固(gu)(gu)(gu)(gu)溶(rong)(rong)(rong)(rong)態(tai)的(de)(de)(de)(de)(de)2507 雙(shuang)(shuang)相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)不(bu)(bu)(bu)銹(xiu)鋼(gang)(gang)30℃下(xia)(xia)于(yu)3.5%NaCl溶(rong)(rong)(rong)(rong)液(ye)中(zhong)(zhong)的(de)(de)(de)(de)(de)Nyquist 圖(tu)如圖(tu)5.5所示(shi)(shi)，從圖(tu)中(zhong)(zhong)可(ke)以很明(ming)顯看(kan)出(chu)隨(sui)固(gu)(gu)(gu)(gu)溶(rong)(rong)(rong)(rong)熱處理溫(wen)度(du)的(de)(de)(de)(de)(de)增(zeng)高容(rong)(rong)(rong)(rong)抗(kang)(kang)弧(hu)半(ban)(ban)(ban)徑(jing)(jing)先(xian)增(zeng)大(da)(da)后減(jian)(jian)小(xiao)(xiao)，1050℃時(shi)容(rong)(rong)(rong)(rong)抗(kang)(kang)弧(hu)半(ban)(ban)(ban)徑(jing)(jing)最(zui)大(da)(da)。通常情(qing)況下(xia)(xia)界(jie)面(mian)間(jian)(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)的(de)(de)(de)(de)(de)遷(qian)(qian)移(yi)(yi)(yi)促(cu)進了高頻(pin)區(qu)容(rong)(rong)(rong)(rong)抗(kang)(kang)弧(hu)的(de)(de)(de)(de)(de)形成，容(rong)(rong)(rong)(rong)抗(kang)(kang)弧(hu)與(yu)雙(shuang)(shuang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)層容(rong)(rong)(rong)(rong)抗(kang)(kang)及(ji)金(jin)(jin)(jin)屬材料(liao)溶(rong)(rong)(rong)(rong)解的(de)(de)(de)(de)(de)綜合作(zuo)用有關(guan)，并且金(jin)(jin)(jin)屬－溶(rong)(rong)(rong)(rong)液(ye)界(jie)面(mian)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)轉移(yi)(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)影(ying)響著(zhu)(zhu)容(rong)(rong)(rong)(rong)抗(kang)(kang)弧(hu)半(ban)(ban)(ban)徑(jing)(jing)的(de)(de)(de)(de)(de)大(da)(da)小(xiao)(xiao)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)在金(jin)(jin)(jin)屬－溶(rong)(rong)(rong)(rong)液(ye)界(jie)面(mian)轉移(yi)(yi)(yi)時(shi)受(shou)到的(de)(de)(de)(de)(de)阻(zu)(zu)力越(yue)(yue)強意味(wei)著(zhu)(zhu)容(rong)(rong)(rong)(rong)抗(kang)(kang)弧(hu)半(ban)(ban)(ban)徑(jing)(jing)越(yue)(yue)大(da)(da)，即(ji)意味(wei)著(zhu)(zhu)金(jin)(jin)(jin)屬的(de)(de)(de)(de)(de)抗(kang)(kang)蝕(shi)(shi)(shi)(shi)性(xing)(xing)能越(yue)(yue)優。從圖(tu)5.5容(rong)(rong)(rong)(rong)抗(kang)(kang)弧(hu)半(ban)(ban)(ban)徑(jing)(jing)的(de)(de)(de)(de)(de)改變(bian)趨勢可(ke)知，固(gu)(gu)(gu)(gu)溶(rong)(rong)(rong)(rong)熱處理溫(wen)度(du)升(sheng)(sheng)高使DSS2507的(de)(de)(de)(de)(de)耐蝕(shi)(shi)(shi)(shi)性(xing)(xing)能首先(xian)增(zeng)強而后減(jian)(jian)弱(ruo)，1050℃時(shi)2507雙(shuang)(shuang)相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)不(bu)(bu)(bu)銹(xiu)鋼(gang)(gang)的(de)(de)(de)(de)(de)抗(kang)(kang)腐蝕(shi)(shi)(shi)(shi)性(xing)(xing)能最(zui)優。不(bu)(bu)(bu)同固(gu)(gu)(gu)(gu)溶(rong)(rong)(rong)(rong)態(tai)的(de)(de)(de)(de)(de)2507雙(shuang)(shuang)相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)不(bu)(bu)(bu)銹(xiu)鋼(gang)(gang)于(yu)3.5%NaCl溶(rong)(rong)(rong)(rong)液(ye)中(zhong)(zhong)的(de)(de)(de)(de)(de)等(deng)效(xiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)如圖(tu)5.6所示(shi)(shi)，采用的(de)(de)(de)(de)(de)是R(C(R(CR))).Rs指參比(bi)(bi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)和(he)工(gong)作(zuo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)間(jian)(jian)的(de)(de)(de)(de)(de)溶(rong)(rong)(rong)(rong)液(ye)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)；Cd1為(wei)雙(shuang)(shuang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)層電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)；Rct為(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)轉移(yi)(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)，其(qi)值(zhi)能夠反應(ying)(ying)(ying)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化(hua)(hua)(hua)(hua)學(xue)反應(ying)(ying)(ying)過程中(zhong)(zhong)透過電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)以及(ji)于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)解質溶(rong)(rong)(rong)(rong)液(ye)中(zhong)(zhong)兩相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)界(jie)面(mian)遷(qian)(qian)移(yi)(yi)(yi)難易的(de)(de)(de)(de)(de)大(da)(da)小(xiao)(xiao)，也能夠反映(ying)金(jin)(jin)(jin)屬發(fa)生(sheng)腐蝕(shi)(shi)(shi)(shi)反應(ying)(ying)(ying)的(de)(de)(de)(de)(de)快慢(man)，一(yi)般(ban)情(qing)況下(xia)(xia)Rct值(zhi)越(yue)(yue)高意味(wei)著(zhu)(zhu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)遷(qian)(qian)移(yi)(yi)(yi)過程中(zhong)(zhong)所受(shou)的(de)(de)(de)(de)(de)阻(zu)(zu)力越(yue)(yue)強，即(ji)材料(liao)的(de)(de)(de)(de)(de)耐腐蝕(shi)(shi)(shi)(shi)性(xing)(xing)能越(yue)(yue)好；Cf表(biao)(biao)(biao)示(shi)(shi)鈍化(hua)(hua)(hua)(hua)膜(mo)(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)，Rf表(biao)(biao)(biao)示(shi)(shi)鈍化(hua)(hua)(hua)(hua)膜(mo)(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)。采用ZsimpWin軟件對等(deng)效(xiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)模擬計(ji)算(suan)得(de)(de)到各元件的(de)(de)(de)(de)(de)數值(zhi)如表(biao)(biao)(biao)5.2所列。從表(biao)(biao)(biao)中(zhong)(zhong)看(kan)出(chu)雙(shuang)(shuang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)層電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)（Cdl)及(ji)鈍化(hua)(hua)(hua)(hua)膜(mo)(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)(rong)(rong)（Cr)隨(sui)固(gu)(gu)(gu)(gu)溶(rong)(rong)(rong)(rong)溫(wen)度(du)的(de)(de)(de)(de)(de)升(sheng)(sheng)高呈(cheng)先(xian)減(jian)(jian)小(xiao)(xiao)后增(zeng)大(da)(da)的(de)(de)(de)(de)(de)趨勢；電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)轉移(yi)(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)（Rct)和(he)鈍化(hua)(hua)(hua)(hua)膜(mo)(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)（Rf)呈(cheng)先(xian)變(bian)大(da)(da)后減(jian)(jian)小(xiao)(xiao)的(de)(de)(de)(de)(de)趨勢，即(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化(hua)(hua)(hua)(hua)學(xue)反應(ying)(ying)(ying)阻(zu)(zu)力隨(sui)固(gu)(gu)(gu)(gu)溶(rong)(rong)(rong)(rong)熱處理溫(wen)度(du)的(de)(de)(de)(de)(de)增(zeng)高先(xian)增(zeng)強后減(jian)(jian)弱(ruo)，2507雙(shuang)(shuang)相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)不(bu)(bu)(bu)銹(xiu)鋼(gang)(gang)的(de)(de)(de)(de)(de)抗(kang)(kang)腐蝕(shi)(shi)(shi)(shi)性(xing)(xing)能表(biao)(biao)(biao)現(xian)為(wei)先(xian)增(zeng)強后減(jian)(jian)弱(ruo)。1000℃時(shi)鋼(gang)(gang)的(de)(de)(de)(de)(de)相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)界(jie)處有σ相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)析出(chu)，σ相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)硬(ying)而脆降低了鋼(gang)(gang)表(biao)(biao)(biao)面(mian)鈍化(hua)(hua)(hua)(hua)膜(mo)(mo)(mo)的(de)(de)(de)(de)(de)穩定(ding)，表(biao)(biao)(biao)現(xian)為(wei)具有較低的(de)(de)(de)(de)(de)鈍化(hua)(hua)(hua)(hua)膜(mo)(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)（Rf);1050℃時(shi)鋼(gang)(gang)中(zhong)(zhong)的(de)(de)(de)(de)(de)兩相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)比(bi)(bi)例約為(wei)1:1,兩相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)分布較均勻且成分穩定(ding)有利(li)于(yu)鈍化(hua)(hua)(hua)(hua)膜(mo)(mo)(mo)的(de)(de)(de)(de)(de)穩定(ding)，具體(ti)表(biao)(biao)(biao)現(xian)為(wei)鈍化(hua)(hua)(hua)(hua)膜(mo)(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)（Rf)值(zhi)較高，表(biao)(biao)(biao)明(ming)此刻(ke)離(li)子遷(qian)(qian)移(yi)(yi)(yi)時(shi)所受(shou)阻(zu)(zu)力較大(da)(da)，進而2507雙(shuang)(shuang)相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)不(bu)(bu)(bu)銹(xiu)鋼(gang)(gang)的(de)(de)(de)(de)(de)抗(kang)(kang)腐蝕(shi)(shi)(shi)(shi)能力最(zui)佳(jia)；固(gu)(gu)(gu)(gu)溶(rong)(rong)(rong)(rong)熱處理溫(wen)度(du)的(de)(de)(de)(de)(de)進一(yi)步升(sheng)(sheng)高使鋼(gang)(gang)中(zhong)(zhong)的(de)(de)(de)(de)(de)兩相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)比(bi)(bi)例失調，表(biao)(biao)(biao)現(xian)為(wei)鐵素體(ti)相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)含量大(da)(da)幅(fu)升(sheng)(sheng)高，奧氏體(ti)相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)含量減(jian)(jian)小(xiao)(xiao)，不(bu)(bu)(bu)利(li)于(yu)鋼(gang)(gang)表(biao)(biao)(biao)面(mian)鈍化(hua)(hua)(hua)(hua)膜(mo)(mo)(mo)的(de)(de)(de)(de)(de)穩定(ding)，導致(zhi)鈍化(hua)(hua)(hua)(hua)膜(mo)(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)（Rf)減(jian)(jian)小(xiao)(xiao)，實際(ji)表(biao)(biao)(biao)現(xian)為(wei)鋼(gang)(gang)的(de)(de)(de)(de)(de)抗(kang)(kang)蝕(shi)(shi)(shi)(shi)性(xing)(xing)能下(xia)(xia)降，這與(yu)動電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位掃(sao)描獲得(de)(de)的(de)(de)(de)(de)(de)結論(lun)相(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)同。