本文選題：無間隙原子鋼　切入點(diǎn)：梯度納米結(jié)構(gòu)　出處：《中國科學(xué)技術(shù)大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：無間隙原子(IF)鋼具有優(yōu)良的深沖成形性能,廣泛應(yīng)用于汽車、家電等外板制造,是最重要的結(jié)構(gòu)材料之一。但是,IF鋼的耐蝕性較差,服役過程中很容易受到環(huán)境侵蝕而失效。Zn-Al合金防護(hù)涂層具有優(yōu)良的耐蝕和耐磨性能,是最常用的延長鋼鐵結(jié)構(gòu)件服役壽命的涂層材料之一。作為一種新型的涂層制備技術(shù),冷噴涂可以在低溫下實(shí)現(xiàn)涂層的沉積,在金屬涂層制備領(lǐng)域具有廣闊的應(yīng)用前景。如何制備致密穩(wěn)定的保護(hù)性涂層、以及如何提高涂層與基體之間的結(jié)合強(qiáng)度,是冷噴涂技術(shù)發(fā)展中的關(guān)鍵問題。本文利用冷噴涂技術(shù)在IF鋼表面成功制備出致密的Zn-Al涂層,研究了后續(xù)退火處理和IF鋼基體表面納米化對(duì)涂層/基體界面結(jié)合強(qiáng)度的影響。利用金相顯微鏡、掃描電子顯微鏡、透射電子顯微鏡、能譜儀和X射線衍射表征了涂層、基體及界面化合物的微觀組織、成分分布和相組成;利用顯微硬度計(jì)、納米壓痕儀、摩擦磨損試驗(yàn)機(jī)和三電極系統(tǒng)評(píng)價(jià)了退火前后Zn-Al涂層的力學(xué)性能和耐蝕性能;利用三點(diǎn)彎曲和“拔釘法” (Studpull-offtest)研究了涂層/基體之間的結(jié)合強(qiáng)度。得出以下主要結(jié)論:1.利用冷噴涂技術(shù)在IF鋼基體上制備出孔隙率0.5%的Zn-Al合金涂層,制備過程中未發(fā)生明顯的氧化和相變。200-350 ℃溫度范圍內(nèi),涂層硬度隨退火溫度的升高逐漸增大;而涂層的摩擦磨損性能隨退火溫度的升高呈現(xiàn)下降趨勢;退火后涂層的耐腐蝕性能變化不大。2.冷噴涂Zn-Al層的IF鋼原始樣品(Zn-Al/IF-CG)在400 ℃保溫60 min退火后,涂層與基體之間的抗剝離能力略有提高;保溫時(shí)間大于60 min后,涂層與基體界面形成Fe11Zn40、FeZn10和Fe2Al5-xZnx組成的混合化合物相,導(dǎo)致其抗剝離能力隨退火時(shí)間的延長快速降低。3. SMAT處理能夠在IF鋼基體表面制備出梯度納米結(jié)構(gòu)組織,最表層平均晶粒尺寸～10 nm,硬度較粗晶基體提高～33%。表層梯度納米結(jié)構(gòu)組織在400℃以下具有良好的熱穩(wěn)定性。4. IF鋼基體SMAT能夠顯著改善涂層/基體的界面結(jié)合性能,冷噴狀態(tài)下Zn-Al層與SMAT樣品(Zn-Al/IF-SMAT)的界面結(jié)合強(qiáng)度達(dá)到58.1MPa,較Zn-Al/IF-CG 樣品提高了～30%。5.冷噴涂Zn-Al/IF-SMAT樣品的界面結(jié)合強(qiáng)度不能通過后續(xù)擴(kuò)散退火處理進(jìn)一步提高。在400 ℃退火時(shí),保溫時(shí)間小于30 min時(shí)涂層/基體界面結(jié)合強(qiáng)度有所降低;隨著保溫時(shí)間的延長,界面結(jié)合強(qiáng)度開始升高并達(dá)到一個(gè)相對(duì)穩(wěn)定值(～50.2 MPa);當(dāng)保溫時(shí)間大于90 min后,涂層-基體界面結(jié)合強(qiáng)度再次降低。6.相同條件退火處理后,冷噴涂Zn-Al層在表面納米化IF鋼基體上的結(jié)合強(qiáng)度均不低于在粗晶IF鋼基體上的結(jié)合強(qiáng)度。
[Abstract]:The interstitial free if) steel is one of the most important structural materials for its excellent deep drawing formability and widely used in the manufacture of automobile, home appliances and other outer plates, but the corrosion resistance of if steel is poor. Zn-Al alloy protective coating is one of the most commonly used coating materials for prolonging the service life of iron and steel structural parts because of its excellent corrosion resistance and wear resistance due to environmental erosion during service. As a new coating preparation technology, Zn-Al alloy protective coating is a new kind of coating material. Cold spraying can achieve coating deposition at low temperature, which has a broad application prospect in the field of metal coating preparation. How to prepare dense and stable protective coating, and how to improve the bonding strength between coating and substrate, It is a key problem in the development of cold spraying technology. In this paper, a compact Zn-Al coating was successfully prepared on the surface of if steel by cold spraying. The effect of subsequent annealing and nanocrystalline on the interface strength of the coating / substrate was studied. The coating was characterized by metallographic microscope, scanning electron microscope, transmission electron microscope, energy spectrometer and X-ray diffraction. The microstructure, composition distribution and phase composition of matrix and interface compounds, the mechanical properties and corrosion resistance of Zn-Al coatings before and after annealing were evaluated by microhardness tester, nano-indentation tester, friction and wear tester and three-electrode system. The bonding strength between coating and substrate was studied by means of three-point bending and studpull-off test. The following main conclusions were drawn: 1.The Zn-Al alloy coating with 0.5% porosity was prepared on if steel substrate by cold spraying. The hardness of the coating increases gradually with the increase of annealing temperature, while the friction and wear properties of the coating decrease with the increase of annealing temperature. After annealing, the corrosion resistance of the coating changed little. 2. After annealing at 400 鈩，

本文編號(hào)：1650448