1. 動(dong)電位極(ji)化(hua)曲線分(fen)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(xiu)鋼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)2507雙相(xiang)(xiang)(xiang)(xiang)(xiang)不(bu)銹鋼于(yu)3.5%NaCl溶液中(zhong)動電位極化后的(de)腐蝕形貌如圖5.4所示，圖中(zhong)深色是鐵(tie)(tie)素(su)體(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)、淺色是奧(ao)(ao)氏體(ti)(ti)(ti)y相(xiang)(xiang)(xiang)(xiang)(xiang)、黑色圓點(dian)是點(dian)蝕坑(keng)。從(cong)(cong)(cong)圖5.4可知點(dian)蝕坑(keng)主要存在(zai)于(yu)鐵(tie)(tie)素(su)體(ti)(ti)(ti)x相(xiang)(xiang)(xiang)(xiang)(xiang)上，這說明奧(ao)(ao)氏體(ti)(ti)(ti)y相(xiang)(xiang)(xiang)(xiang)(xiang)比(bi)(bi)鐵(tie)(tie)素(su)體(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)要穩定(ding)，有著較優的(de)抗(kang)點(dian)腐蝕性能。奧(ao)(ao)氏體(ti)(ti)(ti)γ相(xiang)(xiang)(xiang)(xiang)(xiang)相(xiang)(xiang)(xiang)(xiang)(xiang)比(bi)(bi)于(yu)鐵(tie)(tie)素(su)體(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)有較好的(de)抗(kang)點(dian)蝕性能的(de)原因在(zai)于(yu)元(yuan)素(su)N的(de)作用。元(yuan)素(su)N是奧(ao)(ao)氏體(ti)(ti)(ti)形成元(yuan)素(su)，于(yu)奧(ao)(ao)氏體(ti)(ti)(ti)γ相(xiang)(xiang)(xiang)(xiang)(xiang)中(zhong)的(de)溶解度要比(bi)(bi)在(zai)鐵(tie)(tie)素(su)體(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)中(zhong)的(de)大，此外N能夠讓Cr和Mo元(yuan)素(su)從(cong)(cong)(cong)鐵(tie)(tie)素(su)體(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)遷(qian)移到奧(ao)(ao)氏體(ti)(ti)(ti)γ相(xiang)(xiang)(xiang)(xiang)(xiang)中(zhong)，N顯著影響著這兩種元(yuan)素(su)在(zai)奧(ao)(ao)氏體(ti)(ti)(ti)γ相(xiang)(xiang)(xiang)(xiang)(xiang)和鐵(tie)(tie)素(su)體(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)中(zhong)的(de)分配，兩相(xiang)(xiang)(xiang)(xiang)(xiang)中(zhong)合金元(yuan)素(su)含量(liang)(liang)的(de)差值隨N元(yuan)素(su)含量(liang)(liang)的(de)增多而降低，所以(yi)奧(ao)(ao)氏體(ti)(ti)(ti)γ相(xiang)(xiang)(xiang)(xiang)(xiang)的(de)點(dian)蝕電位較鐵(tie)(tie)素(su)體(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)要高(gao)，從(cong)(cong)(cong)而蝕坑(keng)較先在(zai)Eb相(xiang)(xiang)(xiang)(xiang)(xiang)對比(bi)(bi)較低的(de)鐵(tie)(tie)素(su)體(ti)(ti)(ti)α相(xiang)(xiang)(xiang)(xiang)(xiang)中(zhong)產生。

2. 交(jiao)流阻(zu)抗測(ce)試分析

  1000℃、1050℃、1100℃、1150℃及(ji)1200℃固溶(rong)(rong)(rong)態(tai)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)2507 雙(shuang)(shuang)(shuang)相(xiang)(xiang)(xiang)(xiang)不(bu)銹(xiu)鋼(gang)(gang)(gang)30℃下(xia)(xia)于(yu)3.5%NaCl溶(rong)(rong)(rong)液(ye)(ye)(ye)中(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)Nyquist 圖(tu)(tu)(tu)如圖(tu)(tu)(tu)5.5所(suo)(suo)示，從圖(tu)(tu)(tu)中(zhong)(zhong)可以很明(ming)顯看(kan)出隨固溶(rong)(rong)(rong)熱(re)處(chu)(chu)理(li)溫度的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)增(zeng)(zeng)高(gao)容(rong)抗弧(hu)半(ban)徑先(xian)(xian)增(zeng)(zeng)大后(hou)減(jian)(jian)(jian)小(xiao)，1050℃時(shi)(shi)(shi)容(rong)抗弧(hu)半(ban)徑最(zui)大。通常情況下(xia)(xia)界(jie)(jie)(jie)面(mian)(mian)間(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)遷移(yi)(yi)促進(jin)了高(gao)頻區容(rong)抗弧(hu)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)形成(cheng)(cheng)，容(rong)抗弧(hu)與雙(shuang)(shuang)(shuang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)層(ceng)容(rong)抗及(ji)金屬(shu)材(cai)料(liao)溶(rong)(rong)(rong)解(jie)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)綜(zong)合作用(yong)有關(guan)，并且金屬(shu)－溶(rong)(rong)(rong)液(ye)(ye)(ye)界(jie)(jie)(jie)面(mian)(mian)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷轉移(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)影響(xiang)著(zhu)(zhu)(zhu)容(rong)抗弧(hu)半(ban)徑的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)大小(xiao)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷在金屬(shu)－溶(rong)(rong)(rong)液(ye)(ye)(ye)界(jie)(jie)(jie)面(mian)(mian)轉移(yi)(yi)時(shi)(shi)(shi)受到(dao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)阻(zu)(zu)(zu)(zu)力越(yue)強意(yi)味著(zhu)(zhu)(zhu)容(rong)抗弧(hu)半(ban)徑越(yue)大，即(ji)意(yi)味著(zhu)(zhu)(zhu)金屬(shu)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)抗蝕(shi)(shi)(shi)性能越(yue)優。從圖(tu)(tu)(tu)5.5容(rong)抗弧(hu)半(ban)徑的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)改(gai)變(bian)趨勢可知(zhi)，固溶(rong)(rong)(rong)熱(re)處(chu)(chu)理(li)溫度升(sheng)高(gao)使(shi)DSS2507的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)耐(nai)蝕(shi)(shi)(shi)性能首先(xian)(xian)增(zeng)(zeng)強而后(hou)減(jian)(jian)(jian)弱(ruo)，1050℃時(shi)(shi)(shi)2507雙(shuang)(shuang)(shuang)相(xiang)(xiang)(xiang)(xiang)不(bu)銹(xiu)鋼(gang)(gang)(gang)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)抗腐蝕(shi)(shi)(shi)性能最(zui)優。不(bu)同(tong)固溶(rong)(rong)(rong)態(tai)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)2507雙(shuang)(shuang)(shuang)相(xiang)(xiang)(xiang)(xiang)不(bu)銹(xiu)鋼(gang)(gang)(gang)于(yu)3.5%NaCl溶(rong)(rong)(rong)液(ye)(ye)(ye)中(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)等效(xiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)如圖(tu)(tu)(tu)5.6所(suo)(suo)示，采用(yong)的(de)(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)(dian)極(ji)和工(gong)作電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)間(jian)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)溶(rong)(rong)(rong)液(ye)(ye)(ye)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)；Cd1為(wei)(wei)(wei)雙(shuang)(shuang)(shuang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)層(ceng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)；Rct為(wei)(wei)(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷轉移(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)，其值能夠反(fan)應電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化(hua)學反(fan)應過程(cheng)(cheng)中(zhong)(zhong)透(tou)過電(dian)(dian)(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)(dian)(dian)解(jie)質溶(rong)(rong)(rong)液(ye)(ye)(ye)中(zhong)(zhong)兩相(xiang)(xiang)(xiang)(xiang)界(jie)(jie)(jie)面(mian)(mian)遷移(yi)(yi)難(nan)易的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)大小(xiao)，也能夠反(fan)映金屬(shu)發生腐蝕(shi)(shi)(shi)反(fan)應的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)快慢，一般(ban)情況下(xia)(xia)Rct值越(yue)高(gao)意(yi)味著(zhu)(zhu)(zhu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷遷移(yi)(yi)過程(cheng)(cheng)中(zhong)(zhong)所(suo)(suo)受的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)阻(zu)(zu)(zu)(zu)力越(yue)強，即(ji)材(cai)料(liao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)耐(nai)腐蝕(shi)(shi)(shi)性能越(yue)好；Cf表(biao)(biao)(biao)(biao)示鈍(dun)化(hua)膜(mo)(mo)(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)，Rf表(biao)(biao)(biao)(biao)示鈍(dun)化(hua)膜(mo)(mo)(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)。采用(yong)ZsimpWin軟件(jian)對等效(xiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)模(mo)擬計算(suan)得到(dao)各元件(jian)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)數值如表(biao)(biao)(biao)(biao)5.2所(suo)(suo)列。從表(biao)(biao)(biao)(biao)中(zhong)(zhong)看(kan)出雙(shuang)(shuang)(shuang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)層(ceng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)（Cdl)及(ji)鈍(dun)化(hua)膜(mo)(mo)(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)（Cr)隨固溶(rong)(rong)(rong)溫度的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)升(sheng)高(gao)呈(cheng)先(xian)(xian)減(jian)(jian)(jian)小(xiao)后(hou)增(zeng)(zeng)大的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)趨勢；電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷轉移(yi)(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)（Rct)和鈍(dun)化(hua)膜(mo)(mo)(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)（Rf)呈(cheng)先(xian)(xian)變(bian)大后(hou)減(jian)(jian)(jian)小(xiao)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)趨勢，即(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化(hua)學反(fan)應阻(zu)(zu)(zu)(zu)力隨固溶(rong)(rong)(rong)熱(re)處(chu)(chu)理(li)溫度的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)增(zeng)(zeng)高(gao)先(xian)(xian)增(zeng)(zeng)強后(hou)減(jian)(jian)(jian)弱(ruo)，2507雙(shuang)(shuang)(shuang)相(xiang)(xiang)(xiang)(xiang)不(bu)銹(xiu)鋼(gang)(gang)(gang)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)抗腐蝕(shi)(shi)(shi)性能表(biao)(biao)(biao)(biao)現(xian)為(wei)(wei)(wei)先(xian)(xian)增(zeng)(zeng)強后(hou)減(jian)(jian)(jian)弱(ruo)。1000℃時(shi)(shi)(shi)鋼(gang)(gang)(gang)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)相(xiang)(xiang)(xiang)(xiang)界(jie)(jie)(jie)處(chu)(chu)有σ相(xiang)(xiang)(xiang)(xiang)析出，σ相(xiang)(xiang)(xiang)(xiang)硬而脆降低了鋼(gang)(gang)(gang)表(biao)(biao)(biao)(biao)面(mian)(mian)鈍(dun)化(hua)膜(mo)(mo)(mo)(mo)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)穩(wen)定，表(biao)(biao)(biao)(biao)現(xian)為(wei)(wei)(wei)具有較低的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)鈍(dun)化(hua)膜(mo)(mo)(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)（Rf);1050℃時(shi)(shi)(shi)鋼(gang)(gang)(gang)中(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)兩相(xiang)(xiang)(xiang)(xiang)比例(li)約為(wei)(wei)(wei)1:1,兩相(xiang)(xiang)(xiang)(xiang)分布較均勻且成(cheng)(cheng)分穩(wen)定有利于(yu)鈍(dun)化(hua)膜(mo)(mo)(mo)(mo)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)穩(wen)定，具體(ti)(ti)(ti)表(biao)(biao)(biao)(biao)現(xian)為(wei)(wei)(wei)鈍(dun)化(hua)膜(mo)(mo)(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)（Rf)值較高(gao)，表(biao)(biao)(biao)(biao)明(ming)此刻離子遷移(yi)(yi)時(shi)(shi)(shi)所(suo)(suo)受阻(zu)(zu)(zu)(zu)力較大，進(jin)而2507雙(shuang)(shuang)(shuang)相(xiang)(xiang)(xiang)(xiang)不(bu)銹(xiu)鋼(gang)(gang)(gang)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)抗腐蝕(shi)(shi)(shi)能力最(zui)佳；固溶(rong)(rong)(rong)熱(re)處(chu)(chu)理(li)溫度的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)進(jin)一步升(sheng)高(gao)使(shi)鋼(gang)(gang)(gang)中(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)兩相(xiang)(xiang)(xiang)(xiang)比例(li)失(shi)調(diao)，表(biao)(biao)(biao)(biao)現(xian)為(wei)(wei)(wei)鐵素體(ti)(ti)(ti)相(xiang)(xiang)(xiang)(xiang)含(han)量大幅升(sheng)高(gao)，奧(ao)氏體(ti)(ti)(ti)相(xiang)(xiang)(xiang)(xiang)含(han)量減(jian)(jian)(jian)小(xiao)，不(bu)利于(yu)鋼(gang)(gang)(gang)表(biao)(biao)(biao)(biao)面(mian)(mian)鈍(dun)化(hua)膜(mo)(mo)(mo)(mo)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)穩(wen)定，導致鈍(dun)化(hua)膜(mo)(mo)(mo)(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)（Rf)減(jian)(jian)(jian)小(xiao)，實際表(biao)(biao)(biao)(biao)現(xian)為(wei)(wei)(wei)鋼(gang)(gang)(gang)的(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)(de)抗蝕(shi)(shi)(shi)性能下(xia)(xia)降，這與動(dong)電(dian)(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)(de)結論相(xiang)(xiang)(xiang)(xiang)同(tong)。