等离子喷焊复合材料强化层及其组织与性能研究

发布时间：2018-01-19 06:09

本文关键词： 等离子喷焊原位生成金属基复合材料组织性能　出处：《吉林大学》2015年博士论文　论文类型：学位论文

【摘要】：磨损失效是材料表面最常见的失效形式之一,不仅会带来巨大的经济损失,还会造成重大的人员伤亡。表面工程技术(如大气等离子喷涂、高速火焰喷涂、激光熔覆、等离子喷焊等)是改善材料表面性能的有效途径。热喷涂技术,由于涂层内部存在孔隙、涂层与基体之间为机械结合(结合强度低),且涂层厚度受到一定限制,影响其更广泛的应用。激光熔覆设备比较昂贵,维修成本高,并且难于制备大面积的熔覆层,在生产中的应用也受到一定的限制。等离子喷焊具有组织致密、喷焊层/母材界面为冶金结合及喷焊层厚度易于控制等优点,近年来受到工业界的普遍关注。本文采用等离子喷焊技术在Q235低碳钢表面研究制备陶瓷颗粒增强金属基复合材料强化层,并研究其微观组织及性能特点,为改善材料的表面性能提供必要的理论依据和工艺途径。本文首先系统地研究了等离子喷焊参数(喷焊电流I、喷焊距离S、喷焊速度V)对Ni60A喷焊层的表面质量及熔合比的影响规律。结果表明,选择喷焊参数:I=45A-55A、S=12mm-13mm、V=30mm/min-35mm/min有利于改善喷焊层的质量。在此基础上,研究了Ni60A喷焊层的微观组织及性能特点。Ni60A喷焊层主要由γ-Ni、Cr23C6、Cr7C3、Ni3Si、Cr B和Cr5B3相组成,γ-Ni为主要组成相,其次是Cr23C6,Cr7C3、Ni3Si、Cr B和Cr5B3相的含量相对较小。Ni60A喷焊层的耐磨性能明显高于Q235钢母材,其磨损机制主要为显微切削和Cr23C6颗粒的破断。基于Ni60A喷焊层的研究结果,采用Ni60A+Ni Cr-Cr3C2+WC-12Co混合粉末研究制备WC颗粒增强Ni基复合材料喷焊层。研究结果表明,随着混合粉末中Ni Cr-Cr3C2粉末质量分数的增加,促进碳化铬(Cr23C6、Cr7C3)的形核、长大,有利于改善喷焊层的耐磨性;随着WC-12Co粉末质量分数增加,WC颗粒明显增多,但WC-12Co质量分数过大(20%)导致喷焊层中出现未完全熔化的WC粒子,影响喷焊层的耐磨性能。WC颗粒增强Ni基复合材料喷焊层微观组织的突出特点是多边形WC颗粒镶嵌在γ-Ni基体中。WC形成反应的吉布斯自由能较低,在熔池中可以自发进行。WC在熔池中的形核方式主要为均质形核,未熔化的WC粒子也可作为核心促进WC的生长。与Q235母材相比,WC颗粒增强Ni基复合材料喷焊层的硬度和耐磨性明显提高,耐磨性能可提高13倍以上。高硬度的WC颗粒是提高喷焊层耐磨性的主要因素,其磨损机制主要为微切削和粗化的WC颗粒破断。采用Ni60A+Ni Cr-Cr3C2+Ti混合粉末研究制备原位生成Ti C颗粒增强Ni基复合材料喷焊层,喷焊层主要为大量原位生成Ti C颗粒弥散分布在Ni基体中。随着纯Ti和Ni Cr-Cr3C2粉末质量分数的增加,原位生成Ti C颗粒的数量明显增多,但纯Ti粉末的质量分数过大(8.58%)时,喷焊层表面氧化严重,内部出现微小的孔隙。在熔池中Ti C主要为均质形核,Ti-Si-C多元化合物粒子也可作为形核的核心,以小平面生长方式生长。与Q235母材相比,原位生成Ti C颗粒增强Ni基复合材料喷焊层的耐磨性提高15倍以上。这主要与Ti C颗粒/Ni基体界面具有很高的强韧性、抗塑性形变能力和裂纹萌生扩展阻力,且Ni基体可以很好地支撑Ti C颗粒等因素有关。原位生成Ti C颗粒增强Ni基复合材料喷焊层主要的磨损机制为微切削、划擦。采用Ni60A+Ni Cr-Cr3C2+Nb混合粉末研究制备原位生成Nb C颗粒增强Ni基复合材料喷焊层,喷焊层的微观组织特点是大量原位生成Nb C颗粒弥散分布在Ni基体中。随着纯Nb和Ni Cr-Cr3C2粉末质量分数的增加,有利于原位生成Nb C颗粒,但纯Nb粉的质量分数过大(13.08%)时,喷焊层中出现未完全熔化的Nb粒子,影响喷焊层的耐磨性能。Nb C在熔池中主要形核方式为均质形核,也会以未完全熔化的Nb粒子为核心进行异质形核,并以二维形核和螺旋位错的生长方式长大。与Q235钢母材相比,原位生成Nb C颗粒增强Ni基复合材料喷焊层的耐磨性可提高14倍以上,其磨损机制主要为微切削和增强相的脱落。比较三种复合材料喷焊层的性能及制备工艺,Ti C颗粒增强Ni基复合材料喷焊层具有更高的耐磨性能,但由于纯Ti粉的存在影响喷焊过程的稳定性;WC(Nb C)颗粒增强Ni基复合材料喷焊层的制备具有相对好工艺稳定性。
[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.

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB333;TG456

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