噴射電沉積Ni-P-BN(h)-Al2O3復合鍍層的耐腐蝕性能研究
2020-03-17 01:47:35
hualin
45鋼(gang)具有較高的(de)(de)強度和(he)較好(hao)的(de)(de)切削加工(gong)(gong)性(xing)(xing)(xing)，在(zai)機械(xie)制(zhi)造領域廣(guang)泛應用(yong)[1]。電沉(chen)(chen)積(ji)制(zhi)備(bei)復合材(cai)料(liao)，是(shi)利(li)用(yong)電化(hua)(hua)(hua)學(xue)(xue)(xue)原(yuan)理將納米(mi)顆(ke)粒(li)與金屬(shu)離(li)子在(zai)陰極工(gong)(gong)件(jian)表(biao)面(mian)實現共(gong)沉(chen)(chen)積(ji)，并制(zhi)得性(xing)(xing)(xing)能(neng)(neng)(neng)優(you)(you)越的(de)(de)復合材(cai)料(liao)的(de)(de)工(gong)(gong)藝過程(cheng)。研(yan)(yan)究(jiu)(jiu)發(fa)現，采用(yong)電沉(chen)(chen)積(ji)的(de)(de)方法(fa)(fa)在(zai)零件(jian)表(biao)面(mian)制(zhi)備(bei)鍍(du)(du)(du)(du)(du)層(ceng)能(neng)(neng)(neng)提高基體材(cai)料(liao)的(de)(de)耐(nai)(nai)腐蝕(shi)性(xing)(xing)(xing)能(neng)(neng)(neng)，延(yan)長其(qi)(qi)使用(yong)壽命。Ni-P合金具有高硬(ying)度、高耐(nai)(nai)磨性(xing)(xing)(xing)及高耐(nai)(nai)腐蝕(shi)性(xing)(xing)(xing)，使其(qi)(qi)成為廣(guang)泛應用(yong)的(de)(de)鍍(du)(du)(du)(du)(du)層(ceng)材(cai)料(liao)。張欣(xin)穎等(deng)[2]采用(yong)期(qi)望函數法(fa)(fa)對噴射電沉(chen)(chen)積(ji)Ni-P合金鍍(du)(du)(du)(du)(du)層(ceng)的(de)(de)不同工(gong)(gong)藝參數進行了優(you)(you)化(hua)(hua)(hua)；王巍等(deng)[3]在(zai)糠醛裝置的(de)(de)換熱器管(guan)束內外(wai)壁(bi)上驗證了Ni-P鍍(du)(du)(du)(du)(du)層(ceng)具有較好(hao)的(de)(de)耐(nai)(nai)腐蝕(shi)效果(guo)。李法(fa)(fa)順(shun)[4]通過研(yan)(yan)究(jiu)(jiu)Ni-P-BN(h) 化(hua)(hua)(hua)學(xue)(xue)(xue)復合鍍(du)(du)(du)(du)(du)層(ceng)的(de)(de)制(zhi)備(bei)工(gong)(gong)藝，發(fa)現其(qi)(qi)具有較好(hao)的(de)(de)力學(xue)(xue)(xue)性(xing)(xing)(xing)能(neng)(neng)(neng)和(he)耐(nai)(nai)摩擦(ca)性(xing)(xing)(xing)能(neng)(neng)(neng)。曲彥平(ping)等(deng)[5]研(yan)(yan)究(jiu)(jiu)發(fa)現添加Al2O3粒(li)子可以(yi)提高Ni-P復合鍍(du)(du)(du)(du)(du)層(ceng)的(de)(de)耐(nai)(nai)磨性(xing)(xing)(xing)和(he)顯微硬(ying)度；郝(hao)亞麗等(deng)[6]研(yan)(yan)究(jiu)(jiu)了表(biao)面(mian)活化(hua)(hua)(hua)劑的(de)(de)種類(lei)和(he)用(yong)量對Ni-P-Al2O3復合鍍(du)(du)(du)(du)(du)層(ceng)的(de)(de)耐(nai)(nai)腐蝕(shi)性(xing)(xing)(xing)能(neng)(neng)(neng)的(de)(de)影響(xiang)。侯(hou)勇[7]在(zai)汽車用(yong)鎂合金上分(fen)別進行常(chang)規化(hua)(hua)(hua)學(xue)(xue)(xue)鍍(du)(du)(du)(du)(du)和(he)超聲波輔助(zhu)化(hua)(hua)(hua)學(xue)(xue)(xue)鍍(du)(du)(du)(du)(du),制(zhi)備(bei)了兩(liang)種Ni-P-Al2O3鍍(du)(du)(du)(du)(du)層(ceng)，發(fa)現其(qi)(qi)耐(nai)(nai)腐蝕(shi)性(xing)(xing)(xing)均(jun)有提升且超聲波輔助(zhu)化(hua)(hua)(hua)學(xue)(xue)(xue)鍍(du)(du)(du)(du)(du)層(ceng)具有更好(hao)的(de)(de)耐(nai)(nai)腐蝕(shi)性(xing)(xing)(xing)能(neng)(neng)(neng)。
噴(pen)(pen)射(she)電(dian)(dian)沉(chen)(chen)積(ji)(ji)技術是電(dian)(dian)沉(chen)(chen)積(ji)(ji)技術的延伸，其(qi)可提(ti)高電(dian)(dian)沉(chen)(chen)積(ji)(ji)過(guo)程的沉(chen)(chen)積(ji)(ji)速度，細化(hua)沉(chen)(chen)積(ji)(ji)層(ceng)組織[8]，優(you)化(hua)復合鍍層(ceng)的力學性(xing)能(neng)和耐腐蝕(shi)性(xing)能(neng)。噴(pen)(pen)射(she)電(dian)(dian)壓和噴(pen)(pen)射(she)間隙(xi)是噴(pen)(pen)射(she)電(dian)(dian)沉(chen)(chen)積(ji)(ji)加工過(guo)程中的重要參數。因此(ci)，本實驗采用噴(pen)(pen)射(she)電(dian)(dian)沉(chen)(chen)積(ji)(ji)在45鋼(gang)基體表面(mian)制(zhi)備(bei)Ni-P-BN(h)-Al2O3復合鍍層(ceng)，研究噴(pen)(pen)射(she)電(dian)(dian)壓和噴(pen)(pen)射(she)間隙(xi)對(dui)復合鍍層(ceng)的耐腐蝕(shi)性(xing)能(neng)影響。
1 實驗(yan)方法
噴(pen)(pen)射電(dian)(dian)沉(chen)積裝置如圖1所(suo)示。噴(pen)(pen)射電(dian)(dian)沉(chen)積的(de)過程中，由計算機控制的(de)三(san)軸(zhou)數控機床驅動安(an)裝在機床上的(de)噴(pen)(pen)嘴，在水平方向(xiang)上做(zuo)往復運(yun)動，將(jiang)工(gong)作(zuo)電(dian)(dian)源正極(ji)與噴(pen)(pen)嘴上的(de)鎳(nie)棒(bang)相(xiang)連，工(gong)作(zuo)電(dian)(dian)源負極(ji)與待鍍(du)工(gong)件(jian)(jian)相(xiang)連，接(jie)通電(dian)(dian)源，由水泵將(jiang)鍍(du)液吸入噴(pen)(pen)嘴，并高速噴(pen)(pen)向(xiang)待鍍(du)工(gong)件(jian)(jian)，多(duo)余鍍(du)液由回液管(guan)輸送回鍍(du)液槽，實(shi)現鍍(du)液的(de)循(xun)環利用。
圖1 噴射電沉積裝置
試件尺寸為(wei)7 mm×8 mm×30 mm的(de)45鋼，其表面經過打磨、電凈除油、強活(huo)化(hua)和弱活(huo)化(hua)等(deng)預處理加工(gong)，用去(qu)離子水(shui)清洗后(hou)吹干(gan)待(dai)用。
利(li)用噴(pen)(pen)射電沉積的(de)方法制(zhi)備Ni-P-BN(h)-Al2O3復(fu)合鍍(du)層，鍍(du)液的(de)成分為(wei)(wei)(wei)：200 g/L NiSO4·6H2O (六(liu)水合硫(liu)酸鎳(nie))、30 g/L NiCl2·6H2O (六(liu)水合氯化鎳(nie))、20 g/L H3PO3 (亞磷(lin)酸)、30 g/L H3BO3 (硼(peng)酸)、60 g/L C6H8O7 (檸(ning)檬酸)、0.01 g/L CH4N2S (硫(liu)脲)、0.08 g/L C12H25SO4Na (十二烷(wan)基硫(liu)酸鈉(na))、8 g/L 50 nm BN(h) 顆粒、1 g/L 30 nm Al2O3顆粒。鍍(du)液的(de)溫度(du)為(wei)(wei)(wei)70 ℃，加工(gong)時(shi)工(gong)件與陽極噴(pen)(pen)嘴的(de)相對運動(dong)速度(du)為(wei)(wei)(wei)1.35 cm/s，加工(gong)的(de)時(shi)間為(wei)(wei)(wei)20 min，實驗的(de)噴(pen)(pen)射間隙為(wei)(wei)(wei)1.6、1.8和(he)2.0 mm，噴(pen)(pen)射電壓(ya)為(wei)(wei)(wei)22，25和(he)28 V。
采(cai)(cai)用(yong)(yong)(yong)Quanta FEI 250掃描(miao)電(dian)鏡 (SEM) 對(dui)復合鍍層腐(fu)蝕(shi)前的(de)表面(mian)形(xing)貌進行觀察。電(dian)化學測(ce)試(shi)(shi)采(cai)(cai)用(yong)(yong)(yong)三電(dian)極(ji)體系，試(shi)(shi)件(jian)(jian)為(wei)工(gong)作(zuo)(zuo)電(dian)極(ji)，工(gong)作(zuo)(zuo)面(mian)積為(wei)1 cm2，鉑片(pian)為(wei)輔(fu)助電(dian)極(ji)，飽(bao)和甘汞(gong)電(dian)極(ji) (SCE) 為(wei)參比電(dian)極(ji)，其(qi)(qi)余部分使用(yong)(yong)(yong)EVA熱熔(rong)膠密(mi)封[9]。極(ji)化曲(qu)線(xian)(xian)測(ce)試(shi)(shi)和電(dian)化學阻抗實驗均在室溫(wen)下由(you)CS350電(dian)化學工(gong)作(zuo)(zuo)站完成。測(ce)試(shi)(shi)中腐(fu)蝕(shi)介質(zhi)為(wei)50 g/L的(de)NaCl溶(rong)液(ye)，極(ji)化曲(qu)線(xian)(xian)掃描(miao)速率為(wei)1.5 mV/s，采(cai)(cai)用(yong)(yong)(yong)極(ji)化曲(qu)線(xian)(xian)外延法(fa)得(de)到自(zi)腐(fu)蝕(shi)電(dian)位和自(zi)腐(fu)蝕(shi)電(dian)流密(mi)度等參數。在開路電(dian)位下采(cai)(cai)用(yong)(yong)(yong)電(dian)化學阻抗譜，其(qi)(qi)測(ce)試(shi)(shi)頻(pin)率為(wei)105~10-2 Hz，掃描(miao)方向由(you)高頻(pin)到低頻(pin)，并使用(yong)(yong)(yong)Zview軟件(jian)(jian)對(dui)測(ce)得(de)的(de)阻抗譜擬(ni)合分析。
2 結果(guo)與討論
2.1 復合(he)鍍層(ceng)的表(biao)面形貌
圖2a~c為(wei)(wei)不同噴射電壓(ya)下(xia)Ni-P-BN(h)-Al2O3復(fu)合鍍(du)層(ceng)的(de)(de)表(biao)面(mian)(mian)形(xing)貌。在(zai)噴射電壓(ya)22~28 V的(de)(de)范(fan)圍內，隨著電壓(ya)的(de)(de)增(zeng)大，Ni-P-BN(h)-Al2O3復(fu)合鍍(du)層(ceng)表(biao)面(mian)(mian)的(de)(de)平整程度(du)先提(ti)升后降(jiang)低(di)，胞狀(zhuang)結(jie)(jie)構尺(chi)寸一致(zhi)性(xing)(xing)先增(zeng)強后減弱(ruo)。在(zai)電壓(ya)為(wei)(wei)25 V時，復(fu)合鍍(du)層(ceng)的(de)(de)表(biao)面(mian)(mian)最為(wei)(wei)平整，胞狀(zhuang)結(jie)(jie)構尺(chi)寸一致(zhi)性(xing)(xing)最好。這是因為(wei)(wei)，隨著電壓(ya)的(de)(de)增(zeng)大，晶(jing)(jing)(jing)核(he)的(de)(de)形(xing)成速率與(yu)長(chang)大的(de)(de)速率均增(zeng)大，但(dan)是電壓(ya)低(di)于(yu)(yu)25 V時，晶(jing)(jing)(jing)核(he)的(de)(de)長(chang)大速率低(di)于(yu)(yu)形(xing)成晶(jing)(jing)(jing)核(he)的(de)(de)速率[10]，鍍(du)層(ceng)表(biao)面(mian)(mian)胞狀(zhuang)結(jie)(jie)構的(de)(de)尺(chi)寸一致(zhi)性(xing)(xing)增(zeng)強。而隨著電壓(ya)超過(guo)25 V時，由(you)于(yu)(yu)晶(jing)(jing)(jing)粒的(de)(de)長(chang)大速度(du)過(guo)快，致(zhi)使復(fu)合鍍(du)層(ceng)的(de)(de)表(biao)面(mian)(mian)胞狀(zhuang)結(jie)(jie)構尺(chi)寸一致(zhi)性(xing)(xing)降(jiang)低(di)。
圖2 不(bu)同噴射電(dian)壓(ya)復合(he)鍍(du)層的表面形(xing)貌和不(bu)同噴射間隙復合(he)鍍(du)層的表面形(xing)貌
圖2b、d和e為(wei)不同噴射(she)間(jian)隙(xi)(xi)下Ni-P-BN(h)-Al2O3復合鍍(du)層的(de)(de)(de)(de)表(biao)面(mian)形貌。通(tong)過(guo)對比可(ke)知，在(zai)(zai)噴射(she)間(jian)隙(xi)(xi)1.6~2.0 mm的(de)(de)(de)(de)范圍內，隨著間(jian)隙(xi)(xi)的(de)(de)(de)(de)增(zeng)大，Ni-P-BN(h)-Al2O3復合鍍(du)層的(de)(de)(de)(de)胞狀(zhuang)結(jie)構(gou)的(de)(de)(de)(de)尺寸(cun)稍有(you)增(zeng)大，但是表(biao)面(mian)平整程(cheng)(cheng)度提升(sheng)。在(zai)(zai)間(jian)隙(xi)(xi)為(wei)2.0 mm時(shi)，復合鍍(du)層的(de)(de)(de)(de)表(biao)面(mian)最為(wei)平整。這是因為(wei)，當間(jian)隙(xi)(xi)較(jiao)小時(shi)，復合鍍(du)層的(de)(de)(de)(de)表(biao)面(mian)由于(yu)胞狀(zhuang)結(jie)構(gou)較(jiao)小，在(zai)(zai)胞狀(zhuang)結(jie)構(gou)的(de)(de)(de)(de)晶界連(lian)接處(chu)的(de)(de)(de)(de)表(biao)面(mian)積增(zeng)大[11]，晶界連(lian)接處(chu)的(de)(de)(de)(de)微小裂紋增(zeng)多，鍍(du)層易受(shou)腐蝕。并且隨著間(jian)隙(xi)(xi)的(de)(de)(de)(de)增(zeng)大，鍍(du)液對待鍍(du)工件噴射(she)的(de)(de)(de)(de)沖擊力(li)減弱，待鍍(du)離子在(zai)(zai)噴射(she)電沉積的(de)(de)(de)(de)過(guo)程(cheng)(cheng)中更加穩定。
2.2 不(bu)同噴(pen)射(she)電壓下復(fu)合鍍層的(de)Tafel極化(hua)曲線(xian)
利用電(dian)化(hua)(hua)(hua)學工作站測復(fu)合鍍(du)層(ceng)的(de)極化(hua)(hua)(hua)曲(qu)線(xian)，并使(shi)用工作站自(zi)帶的(de)corrtest軟件(jian)，采(cai)用Tafel極化(hua)(hua)(hua)曲(qu)線(xian)外延法可以得到極化(hua)(hua)(hua)曲(qu)線(xian)對(dui)應(ying)的(de)自(zi)腐(fu)蝕電(dian)位、自(zi)腐(fu)蝕電(dian)流密(mi)度和腐(fu)蝕速率，擬合結果(guo)如表1所示。一般來說，自(zi)腐(fu)蝕電(dian)流密(mi)度反映復(fu)合鍍(du)層(ceng)的(de)腐(fu)蝕速度[12]，其數值越小(xiao)，自(zi)腐(fu)蝕電(dian)位發(fa)生正移，則復(fu)合鍍(du)層(ceng)的(de)耐腐(fu)蝕性能越好(hao)[13]。
表1 Ni-P-BN(h)-Al2O3鍍層極化(hua)曲(qu)線分析結(jie)果
不同噴射電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)下(xia)Ni-P-BN(h)-Al2O3鍍(du)(du)(du)層(ceng)的(de)極化曲線如圖3所示(shi)，圖中復合(he)(he)鍍(du)(du)(du)層(ceng)的(de)Tafel曲線均在(zai)(zai)陽極區(qu)發生(sheng)了鈍化現(xian)(xian)象。由(you)圖3和(he)(he)表(biao)1可知，在(zai)(zai)噴射電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)22~28 V的(de)范圍(wei)內，當電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)增大時(shi)，自(zi)腐(fu)蝕(shi)(shi)電(dian)(dian)(dian)(dian)(dian)流(liu)密(mi)度和(he)(he)腐(fu)蝕(shi)(shi)速(su)率先減小后增大，并(bing)且(qie)在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)為(wei)25 V時(shi)達到(dao)最小值，分別為(wei)8.9251×10-6 A/cm2和(he)(he)0.1082 mm/a。這是因(yin)為(wei)，隨著電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)增大，復合(he)(he)鍍(du)(du)(du)層(ceng)表(biao)面(mian)(mian)的(de)平整(zheng)程度先提升后降低，并(bing)且(qie)25 V時(shi)的(de)復合(he)(he)鍍(du)(du)(du)層(ceng)表(biao)面(mian)(mian)最為(wei)平整(zheng)，出現(xian)(xian)的(de)細微孔隙較(jiao)少，NaCl溶液中腐(fu)蝕(shi)(shi)性較(jiao)強的(de)Cl-難以滲入復合(he)(he)鍍(du)(du)(du)層(ceng)表(biao)面(mian)(mian)，并(bing)且(qie)雖然復合(he)(he)鍍(du)(du)(du)層(ceng)在(zai)(zai)25 V時(shi)的(de)自(zi)腐(fu)蝕(shi)(shi)電(dian)(dian)(dian)(dian)(dian)位發生(sheng)負移，但是此(ci)時(shi)復合(he)(he)鍍(du)(du)(du)層(ceng)的(de)鈍化現(xian)(xian)象較(jiao)為(wei)明顯(xian)，表(biao)面(mian)(mian)產生(sheng)了較(jiao)好的(de)鈍化膜，使鍍(du)(du)(du)層(ceng)的(de)腐(fu)蝕(shi)(shi)減弱，自(zi)腐(fu)蝕(shi)(shi)電(dian)(dian)(dian)(dian)(dian)流(liu)密(mi)度和(he)(he)腐(fu)蝕(shi)(shi)速(su)率下(xia)降，復合(he)(he)鍍(du)(du)(du)層(ceng)的(de)耐腐(fu)蝕(shi)(shi)性能最好。
圖3 噴射間隙為1.6 mm時不同噴射電壓條件下復合鍍層的Tafel曲線
不同噴(pen)射(she)間(jian)隙(xi)下(xia)Ni-P-BN(h)-Al2O3鍍(du)(du)(du)層的(de)(de)極化曲線如(ru)圖(tu)4所示。由圖(tu)4和(he)(he)表1可(ke)知，在噴(pen)射(she)間(jian)隙(xi)1.6~2.0 mm的(de)(de)范圍內(nei)，隨(sui)(sui)著間(jian)隙(xi)的(de)(de)增(zeng)大，復(fu)合(he)鍍(du)(du)(du)層的(de)(de)Tafel曲線整體下(xia)移(yi)，自(zi)(zi)腐(fu)蝕(shi)(shi)電位(wei)發生(sheng)正(zheng)移(yi)，自(zi)(zi)腐(fu)蝕(shi)(shi)電流(liu)密度(du)和(he)(he)腐(fu)蝕(shi)(shi)速(su)(su)率逐漸減(jian)小(xiao)，并在間(jian)隙(xi)為(wei)2.0 mm最小(xiao)，分別(bie)為(wei)2.5664×10-6 A/cm2和(he)(he)0.0311 mm/a，此時復(fu)合(he)鍍(du)(du)(du)層的(de)(de)耐(nai)腐(fu)蝕(shi)(shi)性(xing)(xing)能最好(hao)。這(zhe)是因(yin)為(wei)，噴(pen)射(she)間(jian)隙(xi)較(jiao)小(xiao)時，兩極間(jian)電流(liu)密度(du)較(jiao)大，此時鍍(du)(du)(du)液的(de)(de)陰極極化作用增(zeng)強(qiang)(qiang)，鍍(du)(du)(du)層表面金屬離子缺乏，過多的(de)(de)電子與氫(qing)結合(he)，產生(sheng)疏松等表面缺陷，使腐(fu)蝕(shi)(shi)性(xing)(xing)較(jiao)強(qiang)(qiang)的(de)(de)Cl-容易滲入復(fu)合(he)鍍(du)(du)(du)層的(de)(de)表面。并且隨(sui)(sui)著間(jian)隙(xi)的(de)(de)增(zeng)大，加工區域的(de)(de)鍍(du)(du)(du)液噴(pen)射(she)壓力逐漸減(jian)小(xiao)，沖擊力對枝晶形成的(de)(de)影(ying)響減(jian)弱[14]。因(yin)此，隨(sui)(sui)著間(jian)隙(xi)的(de)(de)增(zeng)大，復(fu)合(he)鍍(du)(du)(du)層的(de)(de)自(zi)(zi)腐(fu)蝕(shi)(shi)電流(liu)密度(du)和(he)(he)腐(fu)蝕(shi)(shi)速(su)(su)率減(jian)小(xiao)，耐(nai)腐(fu)蝕(shi)(shi)性(xing)(xing)能增(zeng)強(qiang)(qiang)。
圖4 噴射電壓為25 V時不同噴射間隙條件下復合鍍層的Tafel曲線
2.3 復合鍍(du)層的電化學阻抗譜分析
Ni-P-BN(h)-Al2O3復合鍍(du)(du)層(ceng)試樣在(zai)50 g/L的(de)NaCl溶液中，不(bu)同的(de)噴射(she)(she)電壓和(he)噴射(she)(she)間(jian)隙測得的(de)電化學阻抗(kang)譜分別如圖(tu)5和(he)6所(suo)示。由圖(tu)可(ke)知，Ni-P-BN(h)-Al2O3復合鍍(du)(du)層(ceng)的(de)Nyquist曲(qu)線均(jun)呈現(xian)出半圓形(xing)的(de)形(xing)狀，表(biao)現(xian)為單一的(de)容抗(kang)弧(hu)。幾(ji)種(zhong)圖(tu)譜相似是(shi)因為這幾(ji)個鍍(du)(du)層(ceng)的(de)基質(zhi)均(jun)為Ni-P合金鍍(du)(du)層(ceng)，它們(men)與(yu)腐蝕(shi)介質(zhi)NaCl接觸(chu)時(shi)發生的(de)基本(ben)反應是(shi)一致的(de)[15,16]。
圖5 噴射間隙為1.6 mm時不同噴射電壓的Nyquist曲線
從(cong)圖5可以看(kan)出，在(zai)(zai)(zai)噴射(she)電壓(ya)(ya)(ya)22~28 V的(de)(de)范(fan)圍內，隨(sui)著(zhu)電壓(ya)(ya)(ya)的(de)(de)增(zeng)大(da)，容(rong)抗弧(hu)的(de)(de)半徑(jing)先增(zeng)大(da)后減小，并在(zai)(zai)(zai)電壓(ya)(ya)(ya)為(wei)25 V時(shi)，容(rong)抗弧(hu)的(de)(de)半徑(jing)達(da)到(dao)最(zui)大(da)值，這說明隨(sui)著(zhu)電壓(ya)(ya)(ya)的(de)(de)增(zeng)大(da)，復合鍍(du)層的(de)(de)耐(nai)腐(fu)(fu)蝕性能(neng)(neng)先提(ti)升后降低，在(zai)(zai)(zai)電壓(ya)(ya)(ya)為(wei)25 V時(shi)耐(nai)腐(fu)(fu)蝕性能(neng)(neng)最(zui)好。從(cong)圖6可以看(kan)出，在(zai)(zai)(zai)噴射(she)間隙(xi)1.6~2.0 mm的(de)(de)范(fan)圍內，隨(sui)著(zhu)間隙(xi)的(de)(de)增(zeng)大(da)，容(rong)抗弧(hu)的(de)(de)半徑(jing)增(zeng)大(da)，并且在(zai)(zai)(zai)間隙(xi)為(wei)2.0 mm時(shi)，容(rong)抗弧(hu)的(de)(de)半徑(jing)達(da)到(dao)最(zui)大(da)值，這說明隨(sui)著(zhu)間隙(xi)的(de)(de)增(zeng)大(da)，復合鍍(du)層的(de)(de)耐(nai)腐(fu)(fu)蝕性能(neng)(neng)提(ti)升，在(zai)(zai)(zai)間隙(xi)為(wei)2.0 mm時(shi)耐(nai)腐(fu)(fu)蝕性能(neng)(neng)最(zui)好。
圖6 噴射電壓為25 V時不同噴射間隙的Nyquist曲線
圖7是復(fu)合(he)鍍(du)(du)(du)(du)層(ceng)在(zai)(zai)不同(tong)工藝(yi)參數的(de)(de)相位角圖，由(you)圖可知，Bode圖均(jun)表現(xian)為(wei)(wei)一(yi)個時(shi)間常數，腐(fu)蝕(shi)介質(zhi)只與復(fu)合(he)鍍(du)(du)(du)(du)層(ceng)表面發生反應，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極過(guo)程(cheng)主要受(shou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)轉(zhuan)移作用(yong)。圖8為(wei)(wei)經(jing)過(guo)Zview軟件(jian)分(fen)析擬合(he)得到(dao)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化(hua)學(xue)阻(zu)(zu)抗譜的(de)(de)等效(xiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路圖，其(qi)所(suo)得參數如(ru)表2所(suo)示。其(qi)中(zhong)(zhong)，Rs為(wei)(wei)NaCl溶(rong)液電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)，Rp為(wei)(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)轉(zhuan)移電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)，其(qi)大(da)小(xiao)由(you)復(fu)合(he)鍍(du)(du)(du)(du)層(ceng)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)導(dao)率和(he)溶(rong)解(jie)過(guo)程(cheng)中(zhong)(zhong)的(de)(de)極化(hua)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)共同(tong)作用(yong)。CPE為(wei)(wei)常相位角元件(jian)，它(ta)與復(fu)合(he)鍍(du)(du)(du)(du)層(ceng)的(de)(de)雙電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)層(ceng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容有關，當CPE-P等于(yu)1時(shi)，可以等效(xiao)為(wei)(wei)純電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容；CPE-P等于(yu)0時(shi)，等效(xiao)為(wei)(wei)純電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)[17]，在(zai)(zai)這里，CPE是介于(yu)純電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)和(he)純電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容的(de)(de)元件(jian)。由(you)表2可知，在(zai)(zai)噴射電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓22~28 V的(de)(de)范圍內，隨(sui)(sui)著電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓的(de)(de)增(zeng)(zeng)大(da)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)轉(zhuan)移電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)RP先增(zeng)(zeng)大(da)后減小(xiao)，并(bing)在(zai)(zai)25 V時(shi)達到(dao)最(zui)大(da)值。在(zai)(zai)噴射間隙(xi)1.6~2.0 mm的(de)(de)范圍內，隨(sui)(sui)著間隙(xi)的(de)(de)增(zeng)(zeng)大(da)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)轉(zhuan)移電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)RP增(zeng)(zeng)大(da)，在(zai)(zai)噴射間隙(xi)為(wei)(wei)2.0 mm時(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)轉(zhuan)移電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)最(zui)大(da)。由(you)于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)轉(zhuan)移電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)RP反映(ying)復(fu)合(he)鍍(du)(du)(du)(du)層(ceng)的(de)(de)耐(nai)(nai)腐(fu)蝕(shi)性能(neng)，它(ta)的(de)(de)值越大(da)，則復(fu)合(he)鍍(du)(du)(du)(du)層(ceng)耐(nai)(nai)腐(fu)蝕(shi)性能(neng)越好[18]，因此，在(zai)(zai)噴射電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓為(wei)(wei)25 V時(shi)，復(fu)合(he)鍍(du)(du)(du)(du)層(ceng)的(de)(de)耐(nai)(nai)腐(fu)蝕(shi)性能(neng)最(zui)好。在(zai)(zai)噴射間隙(xi)為(wei)(wei)2.0 mm時(shi)，復(fu)合(he)鍍(du)(du)(du)(du)層(ceng)的(de)(de)耐(nai)(nai)腐(fu)蝕(shi)性能(neng)最(zui)好。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化(hua)學(xue)阻(zu)(zu)抗譜和(he)等效(xiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路圖的(de)(de)分(fen)析結(jie)果(guo)與極化(hua)曲線的(de)(de)分(fen)析結(jie)果(guo)一(yi)致。
圖7 Ni-P-BN(h)-Al2O3復合(he)鍍層在不同參(can)數的相位角圖
圖8 電化學阻抗譜擬合用等效電路圖
表(biao)2 電化學阻抗譜各(ge)元(yuan)件等效電路(lu)擬合值(zhi)
3 結論
(1) 通過掃(sao)描電鏡(jing)檢(jian)測了復(fu)(fu)(fu)合(he)鍍(du)(du)層(ceng)的表(biao)(biao)(biao)面(mian)(mian)形貌，結(jie)果表(biao)(biao)(biao)明：噴(pen)(pen)(pen)射(she)電壓(ya)(ya)和噴(pen)(pen)(pen)射(she)間(jian)隙的變化對復(fu)(fu)(fu)合(he)鍍(du)(du)層(ceng)的表(biao)(biao)(biao)面(mian)(mian)形貌產(chan)生了影響。在噴(pen)(pen)(pen)射(she)電壓(ya)(ya)22~28 V的范圍內(nei)，隨(sui)著電壓(ya)(ya)的增大，復(fu)(fu)(fu)合(he)鍍(du)(du)層(ceng)的表(biao)(biao)(biao)面(mian)(mian)平整(zheng)程度先提升后(hou)降(jiang)低，胞(bao)狀(zhuang)結(jie)構尺寸(cun)一(yi)致(zhi)性(xing)(xing)先增強后(hou)減小。在電壓(ya)(ya)為(wei)(wei)25 V時，復(fu)(fu)(fu)合(he)鍍(du)(du)層(ceng)的表(biao)(biao)(biao)面(mian)(mian)最為(wei)(wei)平整(zheng)，胞(bao)狀(zhuang)結(jie)構尺寸(cun)一(yi)致(zhi)性(xing)(xing)最好(hao)。在噴(pen)(pen)(pen)射(she)間(jian)隙1.6~2.0 mm的范圍內(nei)，隨(sui)著間(jian)隙的增大，鍍(du)(du)層(ceng)的胞(bao)狀(zhuang)結(jie)構的尺寸(cun)稍有增大，但是表(biao)(biao)(biao)面(mian)(mian)平整(zheng)程度提升。在間(jian)隙為(wei)(wei)2.0 mm時，復(fu)(fu)(fu)合(he)鍍(du)(du)層(ceng)的表(biao)(biao)(biao)面(mian)(mian)最為(wei)(wei)平整(zheng)。
(2) 在(zai)噴射電(dian)(dian)壓(ya)22~28 V的(de)范圍(wei)內(nei)，隨著電(dian)(dian)壓(ya)的(de)增(zeng)大，復合(he)(he)鍍(du)層(ceng)均發(fa)生陽極強化(hua)，自腐(fu)(fu)蝕電(dian)(dian)流(liu)密度(du)和(he)腐(fu)(fu)蝕速(su)率先減(jian)小(xiao)后增(zeng)大，復合(he)(he)鍍(du)層(ceng)的(de)耐腐(fu)(fu)蝕性能先提(ti)升后降低，在(zai)電(dian)(dian)壓(ya)為25 V時(shi)，復合(he)(he)鍍(du)層(ceng)的(de)耐腐(fu)(fu)蝕性能最好。在(zai)噴射間隙(xi)1.6~2.0 mm的(de)范圍(wei)內(nei)，隨著間隙(xi)的(de)增(zeng)大，復合(he)(he)鍍(du)層(ceng)自腐(fu)(fu)蝕電(dian)(dian)位(wei)正移，自腐(fu)(fu)蝕電(dian)(dian)流(liu)密度(du)和(he)腐(fu)(fu)蝕速(su)率減(jian)小(xiao)，復合(he)(he)鍍(du)層(ceng)的(de)耐腐(fu)(fu)蝕性能逐漸提(ti)升，并在(zai)間隙(xi)為2.0 mm時(shi)復合(he)(he)鍍(du)層(ceng)的(de)耐腐(fu)(fu)蝕性能最好。
(3) 在噴(pen)射(she)電(dian)(dian)(dian)壓22~28 V的(de)(de)范(fan)圍(wei)內，隨(sui)(sui)著電(dian)(dian)(dian)壓的(de)(de)增(zeng)大(da)，復合鍍(du)(du)層的(de)(de)阻抗譜曲線(xian)半徑(jing)(jing)大(da)小(xiao)和電(dian)(dian)(dian)荷轉(zhuan)移電(dian)(dian)(dian)阻先增(zeng)大(da)后(hou)減小(xiao)，復合鍍(du)(du)層的(de)(de)耐(nai)腐(fu)蝕性(xing)(xing)能(neng)先提(ti)升后(hou)降低，并在電(dian)(dian)(dian)壓為25 V時(shi)(shi)，曲線(xian)半徑(jing)(jing)最(zui)(zui)(zui)(zui)大(da)，電(dian)(dian)(dian)荷轉(zhuan)移電(dian)(dian)(dian)阻最(zui)(zui)(zui)(zui)大(da)，此時(shi)(shi)復合鍍(du)(du)層的(de)(de)耐(nai)腐(fu)蝕性(xing)(xing)能(neng)最(zui)(zui)(zui)(zui)好。在噴(pen)射(she)間(jian)(jian)隙(xi)(xi)1.6~2.0 mm的(de)(de)范(fan)圍(wei)內，隨(sui)(sui)著間(jian)(jian)隙(xi)(xi)的(de)(de)增(zeng)大(da)，復合鍍(du)(du)層的(de)(de)阻抗譜曲線(xian)半徑(jing)(jing)增(zeng)大(da)，電(dian)(dian)(dian)荷轉(zhuan)移電(dian)(dian)(dian)阻增(zeng)大(da)，復合鍍(du)(du)層的(de)(de)耐(nai)腐(fu)蝕性(xing)(xing)能(neng)逐漸提(ti)升，并在間(jian)(jian)隙(xi)(xi)為2.0 mm時(shi)(shi)最(zui)(zui)(zui)(zui)大(da)，此時(shi)(shi)復合鍍(du)(du)層的(de)(de)耐(nai)腐(fu)蝕性(xing)(xing)能(neng)最(zui)(zui)(zui)(zui)好。