本文關(guān)鍵詞： 團(tuán)聚體 納米等離子涂層 孔隙及裂紋 重熔 點(diǎn)蝕 鈍化　出處：《上海大學(xué)》2016年博士論文　論文類型：學(xué)位論文

【摘要】：本文以Cu、FeCr、NiAl、FeSi四種納米粉體為原料,制備Cu、FeCr、NiAl、FeSi四種納米等離子涂層,并對(duì)四種納米等離子涂層進(jìn)行重熔處理。本文主要開(kāi)展的工作如下:本文首先通過(guò)噴霧造粒法及等離子噴涂技術(shù),制備出Cu、FeCr、NiAl、FeSi四種納米等離子涂層,并對(duì)其內(nèi)部結(jié)構(gòu)及相關(guān)性能進(jìn)行初步測(cè)試分析;為了進(jìn)一步優(yōu)化四種納米等離子涂層內(nèi)部結(jié)構(gòu)、耐腐蝕性能及機(jī)械性能,將Cu、FeCr、NiAl、FeSi四種納米等離子涂層分別在850℃、900℃、950℃、1000℃,1050℃、1100℃、1150℃、1200℃,650℃、700℃、750℃、800℃,1100℃、1150℃、1200℃、1250℃溫度進(jìn)行氫氣氣氛下整體加熱重熔處理,并分別對(duì)四種納米等離子涂層在內(nèi)部微觀形貌及結(jié)構(gòu)、耐腐蝕性能及機(jī)械性能方面進(jìn)行測(cè)試分析,以期得到具有更好內(nèi)部結(jié)構(gòu)及性能的等離子涂層;此外,為了進(jìn)一步研究納米等離子涂層在3.5%(wt.)NaCl溶液中的腐蝕機(jī)理,通過(guò)掃描電化學(xué)顯微鏡(SECM)對(duì)四種涂層微觀點(diǎn)蝕性能進(jìn)行測(cè)試分析,從而揭示納米等離子涂層在腐蝕溶液中的點(diǎn)蝕過(guò)程及機(jī)理;另外,對(duì)四種納米等離子涂層在硼酸緩沖液中的鈍化現(xiàn)象及鈍化膜性能進(jìn)行了研究;最后,通過(guò)materials studio軟件對(duì)四種納米等離子涂層熱處理工藝進(jìn)行了模擬,從而在分子動(dòng)力學(xué)及表面能的層面對(duì)納米等離子涂層在熱處理過(guò)程中的結(jié)構(gòu)及性能的變化,以及對(duì)涂層內(nèi)部結(jié)構(gòu)對(duì)涂層晶粒弛豫現(xiàn)象的影響進(jìn)行理論研究,通過(guò)以上幾個(gè)方面的研究,主要得到的結(jié)論如下:通過(guò)噴霧造粒法對(duì)四種納米粉體進(jìn)行了團(tuán)聚處理,團(tuán)聚體具有良好的質(zhì)量及流動(dòng)性,適宜直接作為等離子噴涂的噴涂材料;通過(guò)等離子技術(shù)直接將團(tuán)聚體作為噴涂材料噴涂至Q235低碳鋼表面,制備出四種納米等離子涂層,通過(guò)對(duì)涂層微觀形貌及性能的研究發(fā)現(xiàn),納米等離子涂層內(nèi)部結(jié)構(gòu)表現(xiàn)出明顯的雙重特性,即納米等離子涂層由未熔化的納米級(jí)顆粒及熔化部分構(gòu)成,未熔化的納米級(jí)顆粒之間及納米級(jí)顆粒與熔化部分界面處存在細(xì)小縫隙,這些細(xì)小縫隙在納米等離子涂層中形成孔隙及裂紋,所以,納米等離子涂層中存在孔隙及裂紋的原因是由于涂層中未熔化納米級(jí)顆粒的存在。將Cu、FeCr、NiAl、FeSi四種納米等離子涂層分別在850℃、900℃、950℃、1000℃,1050℃、1100℃、1150℃、1200℃,650℃、700℃、750℃、800℃,1100℃、1150℃、1200℃、1250℃溫度進(jìn)行氫氣氣氛下重熔處理發(fā)現(xiàn),Cu、FeCr、NiAl、fesi四種納米等離子涂層分別在950℃、1150℃、700℃、1200℃下進(jìn)行重熔處理后,涂層內(nèi)部納米級(jí)顆粒被消除,涂層內(nèi)部形成單一致密的結(jié)構(gòu),從而使涂層中的孔隙及裂紋明顯減少甚至消除,涂層的耐腐蝕性能及機(jī)械性能顯著提高。四種納米等離子涂層在3.5%(wt.)nacl溶液中發(fā)生點(diǎn)蝕現(xiàn)象的主要原因是由于涂層中存在孔隙及裂紋,涂層結(jié)構(gòu)不致密所致,溶液通過(guò)納米等離子涂層中的孔隙及裂紋進(jìn)入涂層內(nèi)部并對(duì)低碳鋼基體進(jìn)行腐蝕,從而在樣品表面形成點(diǎn)蝕;納米等離子涂層在3.5%(wt.)nacl溶液中的腐蝕包括兩種腐蝕行為,即點(diǎn)蝕及均勻腐蝕,均勻腐蝕是由于涂層本身被腐蝕產(chǎn)生的,而這種腐蝕產(chǎn)生的電流遠(yuǎn)小于點(diǎn)蝕所產(chǎn)生的電流,且均勻腐蝕產(chǎn)生的電流并不隨著重熔溫度的不同及浸泡時(shí)間的不同而發(fā)生明顯的變化,說(shuō)明納米等離子涂層在不同溫度重熔處理后及在溶液中不同浸泡時(shí)間所表現(xiàn)的耐腐蝕性能的強(qiáng)弱主要是由于點(diǎn)蝕行為的不同;納米等離子涂層在3.5%(wt.)nacl溶液浸泡過(guò)程中,涂層中孔隙及裂紋較大的地方點(diǎn)蝕程度容易隨著浸泡時(shí)間的延長(zhǎng)逐漸增強(qiáng),而一些孔隙及裂紋較小的地方,點(diǎn)蝕現(xiàn)象容易隨著浸泡時(shí)間的延長(zhǎng)減弱甚至消失,這主要是點(diǎn)蝕產(chǎn)生的不溶性生成物會(huì)將孔隙及裂紋堵塞所致;cu、fecr、nial、fesi四種納米等離子噴涂樣品分別在950℃、1150℃、700℃、1200℃溫度下重熔處理后具有最好的耐點(diǎn)蝕性能,這主要是由于在這些溫度下重熔處理后涂層孔隙及裂紋較少,涂層致密性及均勻性較好。對(duì)低碳鋼基體及分別在950℃、1150℃、700℃、1200℃溫度下重熔處理后的cu、fecr、nial、fesi納米等離子涂層在硼酸緩沖液中進(jìn)行動(dòng)電位極化曲線、恒電位陽(yáng)極鈍化及mott-schottky進(jìn)行研究可知,四種納米等離子涂層在硼酸緩沖液中均出現(xiàn)鈍化現(xiàn)象,且四種經(jīng)過(guò)以上溫度重熔處理后的涂層維鈍電流均較低碳鋼偏小;四種納米等離子涂層在硼酸緩沖溶液中恒電位陽(yáng)極鈍化過(guò)程中產(chǎn)生較為致密的鈍化膜,這種鈍化膜可以有效屏蔽電荷的通過(guò),而低碳鋼則形成較為疏松多孔的鈍化膜,這種鈍化膜不能有效的對(duì)電荷產(chǎn)生屏蔽作用,四種納米等離子涂層在硼酸緩沖溶液中形成p型半導(dǎo)體,而低碳鋼則形成n型半導(dǎo)體,且四種納米等離子涂層鈍化膜載流子密度均較低碳鋼明顯偏小。對(duì)cu、fecr、nial、fesi四種納米等離子涂層分別在850℃、900℃、950℃、1000℃,1050℃、1100℃、1150℃、1200℃,650℃、700℃、750℃、800℃,1100℃、1150℃、1200℃、1250℃溫度下重熔進(jìn)行materials studio模擬發(fā)現(xiàn),Cu、FeCr、NiAl、FeSi四種納米等離子涂層分別在950℃、1150℃、700℃、1200℃溫度下重熔處理后其表面能最小。說(shuō)明四種納米等離子涂層分別在950℃、1150℃、700℃、1200℃溫度下重熔處理后涂層最穩(wěn)定,涂層內(nèi)部缺陷最少;將模擬實(shí)驗(yàn)與重熔實(shí)驗(yàn)進(jìn)行對(duì)比分析可以看出,模擬狀態(tài)下的四種最佳熱處理溫度與重熔實(shí)驗(yàn)中最佳重熔溫度吻合,這說(shuō)明經(jīng)過(guò)最佳重熔處理后,納米等離子涂層內(nèi)部未熔化納米級(jí)顆粒被消除,涂層致密度增強(qiáng),從而有效降低了涂層內(nèi)部晶粒的弛豫現(xiàn)象。
[Abstract]:In this paper, Cu, FeCr, NiAl, FeSi four nano powder as raw materials, preparation of Cu, FeCr, NiAl, FeSi four nano coating, and four kinds of nano coating of plasma remelting. The main work is as follows: firstly, by spray granulation and plasma spraying technology, preparation Cu, FeCr, NiAl, FeSi four nano coating, and the performance of its internal structure and preliminary test analysis; in order to further optimize the internal structure of four kinds of nano coating, corrosion resistance and mechanical properties, corrosion resistance to Cu, FeCr, NiAl, FeSi four nano plasma coating respectively at 850 C, 900 C, 950 C, 1000 C, 1050 C, 1100 C, 1150 C, 1200 C, 650 C, 700 C, 750 C, 800 C, 1100 C, 1150 C, 1200 C, 1250 C temperature under hydrogen atmosphere heating remelting, and respectively to four kinds of nano coating in micro plasma the morphology and The structure, properties and mechanical properties of corrosion resistance are analyzed in order to get better performance with plasma coating structure and internal; in addition, in order to further study the nano coating on the plasma 3.5% (wt.) corrosion mechanism in NaCl solution, by scanning electrochemical microscopy (SECM) were tested on four kinds of coating micro pitting the performance, so as to reveal the pitting corrosion process and mechanism of nano coating in corrosion solution; in addition, the performance of four kinds of nano coating passivation in borate buffer solution and passivation film were studied; finally, through the simulation of four kinds of nano coating heat treatment process of Materials Studio software, so as to change the face of the structure and properties of nano coating during heat treatment in molecular dynamics and surface energy of the coating layer, and the internal structure of the coating grain relaxation Theoretical study of the phenomenon, through the researches above, the main conclusions are as follows: by spray granulation of the reunion of four kinds of nano powder, aggregates with quality and good fluidity, suitable as spraying material for plasma spraying; by plasma technology directly to the aggregates as spraying materials to spray Q235 low carbon steel surface, prepared four kinds of nano coating, through the study on Microstructure and properties of the coatings, the internal structure of nano plasma coating showed double features obvious, namely nano plasma coating consists of nano particles and melting part of unmelted, there are tiny gaps between the nano particles and unmelted nano particles and melting part of the interface, the small gap formation of cracks and pores in the nano coating, so nano plasma Causes of cracks and pores in the coating is due to sub unmelted nano particles in the coating. The Cu, FeCr, NiAl, FeSi four nano plasma coating respectively at 850 C, 900 C, 950 C, 1000 C, 1050 C, 1100 C, 1150 C, 1200 C, 650 C, 700 C, 750 C, 800 C, 1100 C, 1150 C, 1200 C, 1250 C temperature under hydrogen atmosphere remelting treatment, Cu, FeCr, NiAl, FeSi four nano plasma coating respectively at 950 C, 1150 C, 700 C, 1200 C after remelting treatment, coating with nanometer particles by eliminating the internal structure of the coating, to form a single compact, so that the pores in the coating and the crack was reduced or even eliminated, corrosion resistance and mechanical properties of the coating significantly improved. Four kinds of nano plasma coating (wt.) in 3.5% main causes of pitting in the solution of NaCl is due to the presence of cracks and pores in the coating. Coating The dense solution through the pores caused by nano plasma coating in coatings and corrosion and crack into the low carbon steel substrate, resulting in the formation of pitting corrosion on the surface of the sample; in the 3.5% coating nano plasma (wt.) corrosion in NaCl solution includes two kinds of corrosion behavior, namely pitting corrosion and uniform corrosion, uniform corrosion is due to the coating itself the corrosion current and corrosion, this is far less than the current generation of pitting, and uniform corrosion is not different with the remelting temperature and soaking time of different change shows that the nano plasma coating after remelting treatment at different temperatures and different soaking time in solution showed corrosion the performance of the strength is mainly due to the different Pitting Behavior; in the 3.5% coating nano plasma (wt.) NaCl solution soaking process, the pores and cracks of large The local pitting degree easily with the increase of immersion time increased, while some smaller pores and cracks, pitting phenomenon easily with the extension of soaking time, weaken or even disappear, this is mainly pitting corrosion of insoluble material will generate cracks and pores blockage caused by Cu, FeCr, NiAl; FeSi, four kinds of nano plasma spraying the samples were at 950 C, 1150 C, 700 C, at a temperature of 1200 DEG C after the remelting treatment has the best corrosion resistance, which is mainly due to the temperature in the coating after remelting treatment of cracks and pores small, compact coating and good uniformity. The low carbon steel substrate and respectively at 950 degrees, 1150 degrees. 700 C, Cu, after the remelting treatment at a temperature of 1200 DEG C FeCr, NiAl, potentiodynamic polarization curves of FeSi nano coating in boric acid buffer, potentiostatic anodic passivation and Mott-Schottky study shows that the four kinds of nano etc. The passivation phenomenon appeared ion coating in boric acid buffer, and the four kinds of coating after the passivation current temperature after remelting treatment are low carbon steel is small; passivation coating is dense four kinds of nano coating in borate buffer solution of potentiostatic anodic passivation process, the passivation film can effectively shield charge through, and low carbon steel is more porous passivation film formed on the passivation film, can not effectively to charge the shielding effect, the formation of four kinds of P type semiconductor nano coating in boric acid buffer solution, and the formation of low carbon steel is n type semiconductor, and the four kinds of nano carrier density plasma coating passivation film of low carbon steel obviously too small. For Cu, FeCr, NiAl, FeSi four nano plasma coating respectively at 850 C, 900 C, 950 C, 1000 C, 1050 C, 1100 C, 1150 C, 1200 C, 650 C, 700 C, 750 C, 800 C, 1100 C, 1150 C, 1200 C, 1250 C temperature materials studio remelting simulation, Cu, FeCr, NiAl, FeSi four nano plasma coating respectively at 950 C, 1150 C, 700 C, 1200 C temperature after remelting treatment on its surface. The smallest shows four kinds of nano plasma coating respectively at 950 DEG C, 1150 C, 700 C, 1200 C temperature after remelting coating is the most stable, the internal defects of the coating will be at least; simulation experiment and remelting experiments were analyzed as can be seen, the four best fit the best heat treatment temperature and remelting remelting experiments in the simulation condition, indicating that the best after remelting treatment, nano plasma coating internal unmelted nano particles is eliminated, coating density enhanced, thereby effectively reducing the internal coating grain relaxation phenomenon.

【學(xué)位授予單位】：上海大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TG174.4

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