本文關鍵詞： 等離子噴焊 原位生成 金屬基復合材料 組織 性能　出處：《吉林大學》2015年博士論文　論文類型：學位論文

【摘要】：磨損失效是材料表面最常見的失效形式之一,不僅會帶來巨大的經(jīng)濟損失,還會造成重大的人員傷亡。表面工程技術(shù)(如大氣等離子噴涂、高速火焰噴涂、激光熔覆、等離子噴焊等)是改善材料表面性能的有效途徑。熱噴涂技術(shù),由于涂層內(nèi)部存在孔隙、涂層與基體之間為機械結(jié)合(結(jié)合強度低),且涂層厚度受到一定限制,影響其更廣泛的應用。激光熔覆設備比較昂貴,維修成本高,并且難于制備大面積的熔覆層,在生產(chǎn)中的應用也受到一定的限制。等離子噴焊具有組織致密、噴焊層/母材界面為冶金結(jié)合及噴焊層厚度易于控制等優(yōu)點,近年來受到工業(yè)界的普遍關注。本文采用等離子噴焊技術(shù)在Q235低碳鋼表面研究制備陶瓷顆粒增強金屬基復合材料強化層,并研究其微觀組織及性能特點,為改善材料的表面性能提供必要的理論依據(jù)和工藝途徑。本文首先系統(tǒng)地研究了等離子噴焊參數(shù)(噴焊電流I、噴焊距離S、噴焊速度V)對Ni60A噴焊層的表面質(zhì)量及熔合比的影響規(guī)律。結(jié)果表明,選擇噴焊參數(shù):I=45A-55A、S=12mm-13mm、V=30mm/min-35mm/min有利于改善噴焊層的質(zhì)量。在此基礎上,研究了Ni60A噴焊層的微觀組織及性能特點。Ni60A噴焊層主要由γ-Ni、Cr23C6、Cr7C3、Ni3Si、Cr B和Cr5B3相組成,γ-Ni為主要組成相,其次是Cr23C6,Cr7C3、Ni3Si、Cr B和Cr5B3相的含量相對較小。Ni60A噴焊層的耐磨性能明顯高于Q235鋼母材,其磨損機制主要為顯微切削和Cr23C6顆粒的破斷�；贜i60A噴焊層的研究結(jié)果,采用Ni60A+Ni Cr-Cr3C2+WC-12Co混合粉末研究制備WC顆粒增強Ni基復合材料噴焊層。研究結(jié)果表明,隨著混合粉末中Ni Cr-Cr3C2粉末質(zhì)量分數(shù)的增加,促進碳化鉻(Cr23C6、Cr7C3)的形核、長大,有利于改善噴焊層的耐磨性;隨著WC-12Co粉末質(zhì)量分數(shù)增加,WC顆粒明顯增多,但WC-12Co質(zhì)量分數(shù)過大(20%)導致噴焊層中出現(xiàn)未完全熔化的WC粒子,影響噴焊層的耐磨性能。WC顆粒增強Ni基復合材料噴焊層微觀組織的突出特點是多邊形WC顆粒鑲嵌在γ-Ni基體中。WC形成反應的吉布斯自由能較低,在熔池中可以自發(fā)進行。WC在熔池中的形核方式主要為均質(zhì)形核,未熔化的WC粒子也可作為核心促進WC的生長。與Q235母材相比,WC顆粒增強Ni基復合材料噴焊層的硬度和耐磨性明顯提高,耐磨性能可提高13倍以上。高硬度的WC顆粒是提高噴焊層耐磨性的主要因素,其磨損機制主要為微切削和粗化的WC顆粒破斷。采用Ni60A+Ni Cr-Cr3C2+Ti混合粉末研究制備原位生成Ti C顆粒增強Ni基復合材料噴焊層,噴焊層主要為大量原位生成Ti C顆粒彌散分布在Ni基體中。隨著純Ti和Ni Cr-Cr3C2粉末質(zhì)量分數(shù)的增加,原位生成Ti C顆粒的數(shù)量明顯增多,但純Ti粉末的質(zhì)量分數(shù)過大(8.58%)時,噴焊層表面氧化嚴重,內(nèi)部出現(xiàn)微小的孔隙。在熔池中Ti C主要為均質(zhì)形核,Ti-Si-C多元化合物粒子也可作為形核的核心,以小平面生長方式生長。與Q235母材相比,原位生成Ti C顆粒增強Ni基復合材料噴焊層的耐磨性提高15倍以上。這主要與Ti C顆粒/Ni基體界面具有很高的強韌性、抗塑性形變能力和裂紋萌生擴展阻力,且Ni基體可以很好地支撐Ti C顆粒等因素有關。原位生成Ti C顆粒增強Ni基復合材料噴焊層主要的磨損機制為微切削、劃擦。采用Ni60A+Ni Cr-Cr3C2+Nb混合粉末研究制備原位生成Nb C顆粒增強Ni基復合材料噴焊層,噴焊層的微觀組織特點是大量原位生成Nb C顆粒彌散分布在Ni基體中。隨著純Nb和Ni Cr-Cr3C2粉末質(zhì)量分數(shù)的增加,有利于原位生成Nb C顆粒,但純Nb粉的質(zhì)量分數(shù)過大(13.08%)時,噴焊層中出現(xiàn)未完全熔化的Nb粒子,影響噴焊層的耐磨性能。Nb C在熔池中主要形核方式為均質(zhì)形核,也會以未完全熔化的Nb粒子為核心進行異質(zhì)形核,并以二維形核和螺旋位錯的生長方式長大。與Q235鋼母材相比,原位生成Nb C顆粒增強Ni基復合材料噴焊層的耐磨性可提高14倍以上,其磨損機制主要為微切削和增強相的脫落。比較三種復合材料噴焊層的性能及制備工藝,Ti C顆粒增強Ni基復合材料噴焊層具有更高的耐磨性能,但由于純Ti粉的存在影響噴焊過程的穩(wěn)定性;WC(Nb C)顆粒增強Ni基復合材料噴焊層的制備具有相對好工藝穩(wěn)定性。
[Abstract]:Wear failure is one of the most common failure forms of material surface, will not only bring huge economic losses, but also cause great casualties. Surface engineering technology (such as atmospheric plasma spraying, flame spraying, laser cladding, plasma spray welding) is an effective way to improve the surface properties of materials. The thermal spraying, due to the presence of the pore inner coating, mechanical bond between the coating and the substrate (low bonding strength), and the coating thickness is limited, affecting its wider application. Laser cladding equipment is expensive, high maintenance cost, the cladding layer and difficult to prepare large area, the application in the production are also subject to certain restrictions. Plasma spray welding has a compact structure, spray welding layer / base metal metallurgy bonding interface and spraying layer thickness are easy to control, has received widespread attention in industry in recent years. This paper uses the plasma spray welding technology The preparation of ceramic particles on the surface of Q235 on low carbon steel reinforced metal matrix composite strengthened layer, and study its microstructure and properties, and provide a theoretical basis and processes necessary for the improvement of surface properties of materials. This paper systematically studied the plasma spray welding parameters (welding current I, spraying distance S, spray the welding speed of V) influences the surface quality and the fusion of Ni60A spray welding layer ratio. The results show that the choice of welding parameters: I=45A-55A, S=12mm-13mm, V=30mm/min-35mm/min have improved the quality of spray welding layer. On this basis, the study of microstructure and performance characteristics of Ni60A spray welding layer of.Ni60A coating is mainly composed of gamma -Ni, Cr23C6, Cr7C3, Ni3Si, Cr, B and Cr5B3 phases, gamma -Ni as the main phase, followed by Cr23C6, Cr7C3, Ni3Si, Cr, B and Cr5B3 content of the relative wear resistance of smaller.Ni60A spray welding layer was significantly higher than the base metal of Q235 steel, the mill The main wear mechanism was micro cutting and Cr23C6 particle breaking. The results of Ni60A spray welding layer based on Ni matrix composite reinforced with WC particles by spray welding layer using Ni60A+Ni Cr-Cr3C2+WC-12Co mixed powder was studied. The results show that, with the increase of mass fraction of Ni powder Cr-Cr3C2 powder mixture, promote chromium carbide (Cr23C6, Cr7C3 the nucleation, growth), is conducive to improving the wear resistance of spray welding layer; with the increase of mass fraction of WC-12Co powder, WC particles increased significantly, but the mass fraction of WC-12Co is too large (20%) in WC particle is not completely melted the spray welding layer, affect the wear resistance of.WC particles reinforced spraying layer of outstanding characteristic of Ni composite spraying layer microstructure of polygonal particles embedded in WC matrix.WC gamma -Ni formation reaction Gibbs free energy is low in the molten pool can be spontaneous nucleation of.WC in pool type mainly for all Quality of nucleation of WC particles unmelted also can be used as the core to promote the growth of WC. Compared with the parent metal of Q235, hardness and wear resistance of WC particles reinforced Ni matrix composite spray welding layer significantly improved wear resistance can be improved more than 13 times. WC particles with high hardness is the main factors to improve the wear resistance of spray welding layer and the main wear mechanism is micro cutting and coarsening of WC particles broken. Using Ni60A+Ni Cr-Cr3C2+Ti mixed powder preparation of in situ Ti C particle reinforced Ni based composite spray coating, spray welding layer is mainly a large number of in situ Ti C particles dispersed in the Ni matrix. With the increase of pure Ti and Ni Cr-Cr3C2 powder mass fraction, the number of in situ Ti C granules increased significantly, but the mass fraction of pure Ti powder is too large (8.58%), spraying layer surface oxidation serious internal tiny pores. In pool Ti C mainly for homogeneous nucleation, Ti-Si-C yuan Compound particles can also be used as the core of nucleation, the small plane growth mode. Compared with the parent metal of Q235, Ti in situ C particle reinforced Ni composites wear resistance of spray welding layer increased more than 15 times. The main C and Ti particles in /Ni matrix interface and the toughness is high resistance to plastic deformation capacity and crack initiation and propagation resistance, Ni matrix can well support Ti C particles and other factors. In situ Ti particle reinforced C wear mechanism of Ni composite spray welding layer is micro cutting, scratching. Preparation of in situ Nb C particles reinforced Ni composites by spray welding layer Ni60A+Ni Cr-Cr3C2+Nb mixed powder was studied, the microstructure characteristics of spray welding layer is large in situ Nb C particles dispersed in the Ni matrix. With the increase of pure Nb and Ni Cr-Cr3C2 powder mass fraction, is conducive to the formation of Nb in situ C particles, but the mass fraction of the pure Nb powder is too large (13.08%) when the Nb particle is not completely melted the spray welding layer, the wear resistance of.Nb C effect of spray welding layer in the molten pool main nucleation mode for homogeneous nucleation, will not completely melted by Nb particles as the core of heterogeneous nucleation, and growth pattern of two-dimensional nucleation and spiral the dislocation grows up. Compared with the parent metal of Q235 steel, Nb in situ C particle reinforced Ni composites wear resistance of spray welding layer can be increased more than 14 times, the main wear mechanism is micro cutting and enhanced phase loss. Comparison of three kinds of composite coating preparation process and performance of Ti, C particles enhanced Ni composite spray coating has higher wear resistance, but because of the existence of the pure Ti powder influence the stability of spray welding process; WC (Nb C) particle reinforced Ni composites prepared by spray welding layer has a relatively good stability of the process.

【學位授予單位】：吉林大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TB333;TG456

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