激光熔覆涂层的研究现状

综述了激光熔覆耐磨涂层和激光熔覆生物涂层的研究现状,归纳整理了激光熔覆涂层的分类及性能影响因素等相关内容,并为激光熔覆涂层的研究和发展指出了方向。     

激光熔覆在钛合金表面改性中的应用

激光熔覆是现代表面改性制造技术中的一种极有发展前途的高新技术。近年来，激光熔覆技术在钛合金表面改性方面得到了广泛的应用。本文概述了近年来国内外利用激光熔覆技术改善钛合金表面性能的研究与应用现状，提出了激光熔覆技术进一步发展的领域和方向。     

船舶海水管路激光熔覆涂层研究进展

首先分析了海水管路腐蚀失效原因；其次，从激光熔覆耐蚀金属涂层的性能、熔覆金属涂层的工艺以及复杂工件内部熔覆涂层的现状3个方面进行综述；最后，总结并为海水管路激光熔覆涂层的研究和发展指出了方向。     

铜合金表面激光熔覆温度场数值图像模拟分析

对铜合金表面进行激光熔覆镍基合金,能够有效改善铜基件的性能。以镍基合金为熔覆材料,对铜合金基件进行激光熔覆实验;基于有限差分法来构建熔覆过程中温度场数字图像的二维数学模型,对边界条件和基体内部相变潜热做数值化处理;最后对实验实际测量值和模拟计算值进行分析。结果表明,铜合金表面激光熔覆镍基合金的冶金结合良好,证明了提出的温度场计算模型精确度高、稳定可靠。     

激光熔覆焊在离心式压缩机轴头及半联轴器中修复的应用

通过对等离子喷涂和激光熔覆焊修复技术进行性能对比分析，采用激光熔覆焊技术修理的离心式压缩机转子轴头和液压装配式联轴器，经装机运行检验其性能完全满足机组运行要求。     

煤矿机械应用激光熔覆技术的研究与实践

结合现代采煤机械对耐磨、耐蚀性能的技术要求,对采用激光熔覆技术改善工件表面性能的实践进行了总结,重点介绍了激光熔覆技术在截齿、采煤机高速轴、液压支架及掘进机密封套上的应用,对煤矿机械激光熔覆材料的选择也进行了讨论。     

激光熔覆Mo-Si难熔金属硅化物高温涂层的加工工艺、组织与性能

以Mo -Si合金粉末为原料 ,采用激光熔覆技术在奥氏体不锈钢 1Cr1 8Ni9Ti表面上制得了由初生MoSi2 树枝晶、块状FeMoSi初生相及枝晶间MoSi2 /α片层状共晶组织组成的难熔金属硅化物高温复合材料涂层。通过优化激光熔覆加工工艺 ,发现并合理利用激光熔覆过程中的自预热效应和预置Mo、Si粉末在熔池前无激光辐射下的高温反应合成两种影响因素 ,首次实现了无裂纹Mo -Si难熔金属硅化物激光熔覆涂层的制备。涂层组织均匀、致密 ,与基材间为完全冶金结合。涂层具有很高的硬度和优异的高温抗氧化性能     

大型往复压缩机曲轴裂纹的激光熔覆修复

阐述了激光熔覆技术的原理与特点,介绍了应用激光熔覆技术修复大型往复压缩机曲轴曲柄销表面裂纹的简要过程及该曲轴修复后的运行情况。实践证明,激光熔覆技术具有覆层缺陷率低、组织细密、性能优异、与基体结合牢固及在加工过程中对基体的热影响极小、工件变形小等优点。     

大型颚式破碎机偏心轴激光熔覆再制造技术研究

为了实现对大型颚式破碎机偏心轴的激光熔覆再制造修复，采用激光熔覆技术在偏心轴材料40CrMnMo试验轴段上制备铁基熔覆层。通过正交试验选择最佳的工艺参数，研究了最佳工艺参数下的熔覆层组织性能，利用金相显微镜、显微硬度计对熔覆层的金相组织、显微硬度进行了研究，最后成功对偏心轴进行了激光熔覆再制造修复，恢复了尺寸公差，并提高了表面使用性能。经激光熔覆再制造后零件在使用性能和产品质量上都能达到甚至超越新品的水平，但成本仅为新品的三分之一，给客户带来较大的经济效益，为水泥行业的再制造发展提供一种新的先进技术，为循环经济的可持续发展提供动力。     

大型颚式破碎机偏心轴激光熔覆再制造技术研究

为了实现对大型颚式破碎机偏心轴的激光熔覆再制造修复，采用激光熔覆技术在偏心轴材料40CrMnMo试验轴段上制备铁基熔覆层。通过正交试验选择最佳的工艺参数，研究了最佳工艺参数下的熔覆层组织性能，利用金相显微镜、显微硬度计对熔覆层的金相组织、显微硬度进行了研究，最后成功对偏心轴进行了激光熔覆再制造修复，恢复了尺寸公差，并提高了表面使用性能。经激光熔覆再制造后零件在使用性能和产品质量上都能达到甚至超越新品的水平，但成本仅为新品的三分之一，给客户带来较大的经济效益，为水泥行业的再制造发展提供一种新的先进技术，为循环经济的可持续发展提供动力。     

合金组分对金属陶瓷覆层材料性能影响的研究

以Mo粉、FeB合金粉和Fe粉为基本原料，分别加入C，Cr，Ni或同时加入C，Cr，Ni合金元素成分，采用原位反应真空液相烧结工艺，在Q235钢基体上，制备三元硼化物基金属陶瓷覆层材料。研究了合金组分对覆层材料抗弯强度的影响以及对覆层硬度和耐磨性的影响。研究结果表明：在三元硼化物基金属陶瓷覆层中同时加入5％Cr，2％Ni，0．8％C作为合金组分是覆层的最佳组成，此时覆层材料具有高的抗弯强度，覆层的硬度和耐磨性指标优异。     

碳化钨对激光熔覆层组织和耐磨性的影响

采用激光熔覆的方法在Q235钢板表面得到熔覆层,研究了激光熔覆后显微组织的变化、表层显微硬度的变化趋势及其原因及熔覆层抗磨损性能提高的幅度。结果表明：添加WC,可使熔覆层组织细化,硬度和抗磨损性能得到不同程度的提高。     

激光熔覆技术制备新型Al-TiC复合涂层的研究

采用预置激光熔覆技术,将Al-Ti-C混合粉末预置于铝合金基体表面,并在氩气保护下,利用YAG激光器实现了在铝合金表面原位形成Al-TiC复合熔覆层。通过改变激光束能量密度和激光束扫描速度等工艺参数,获得了不同工艺条件下的激光熔覆层,并对其显微组织、物相分布及耐磨性能进行比较研究。结果表明由于激光能量密度和激光束扫描速度不同,所形成的熔覆层中TiC的分布状态有很大差别。随着激光能量密度的增大,TiC分布趋于均匀。当激光束扫描速度为2.5mm/s、激光束能量密度为6.09 J/mm2时,熔覆层具有最高的耐磨性能。     

激光熔覆Fe基高Cr涂层组织及抗CO_2腐蚀性能研究

采用激光熔覆方法制备了Fe-20Cr、Fe-30Cr、Fe-40Cr共3种不同Cr含量的Fe基涂层。用扫描电镜(SEM)和X射线衍射(XRD)分析了涂层的微观组织和物相,借助电化学工作站测试了涂层在含CO2饱和地层水中的腐蚀行为,并与P110套管钢进行了对比。结果表明:激光熔覆Fe基含Cr涂层皆为冶金结合,熔覆层质量良好。在地层水中通入CO2后3种涂层腐蚀趋势变大,但由于表面疏松CaCO3和MgCO3产物的形成,抑制了涂层的腐蚀。低Cr含量的Fe-20Cr涂层具有较高的耐蚀性。Cr含量增加时,由于Cr23C6、Cr7C3等碳化物在晶界处析出,产生晶体贫铬区,进而降低了高Cr含量涂层的耐蚀性,但碳化物析出提高了涂层的硬度。     

Investigation on bi-layer coating with La2(Ti0.2Zr0.2Sn0.2Ce0.2Hf0.2)2O7/YSZ prepared by laser cladding

Thermal barrier coatings are an effective technology for improving the high-temperature performance of hot section components in gas turbine engine. Due to their excellent properties, high-entropy oxides are considered to be promising materials for thermal barrier coatings. Laser cladding is a coating preparation technology and the top coat prepared by laser cladding technology has an important application value for thermal barrier coatings. In this work, to improve the thermal cycling behavior of the La₂(Ti_0.2Zr_0.2Sn_0.2Ce_0.2Hf_0.2)₂O₇ high-entropy oxide coating, a bi-layer coating with the La₂(Ti_0.2Zr_0.2Sn_0.2Ce_0.2Hf_0.2)₂O₇ high-entropy oxide layer and the YSZ layer was designed and fabricated by laser cladding on the NiCoCrAlY alloy surface. The microstructure, phase and mechanical properties of the coating were analyzed by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and micro-hardness and nanoindentation tests, respectively. The results show that a bi-layer La₂(Ti_0.2Zr_0.2Sn_0.2Ce_0.2Hf_0.2)₂O₇/YSZ coating was successfully prepared by the laser cladding method, and shows good bonding at the interface between the layers. The high-entropy oxide layer maintains a relatively stable defective fluorite structure and its microstructure exists in the stable cellular and dendrite crystalline state after laser cladding. The high-entropy oxide layer prepared by laser cladding showed an average elastic modulus of 167 GPa and an average hardness of 1022.8HV in nanoindentation tests. Thermal cycling of the coating was carried out at 1050 °C. Failure of the bi-layer coating occurred after 60 thermal cycles at 1050 °C. Thermal stresses between different layers are calculated during thermal cycling. Due to its excellent mechanical properties, the bi-layer coating with the La₂(Ti_0.2Zr_0.2Sn_0.2Ce_0.2Hf_0.2)₂O₇ high-entropy oxide and YSZ layers is expected to become an effective high-entropy oxide thermal barrier coating.     

Adhesion properties of functionally gradient diamond composite films on medical and tool alloys

We have investigated the adhesion properties of microcrystalline diamond thin films on Ti-Al-V alloy, Co-Cr-Mo alloy and steel. Microcrystalline diamond possesses high hardness, a low coefficient of friction, extreme chemical inertness and biocompatibility; these properties can enhance the performance of metal alloys used in medical implants and in machine tools. We have adopted three methods for improving the adhesion of microcrystalline diamond to commonly used metal alloys: (1) by alloying the substrate surface to minimize graphitization; (2) by employing appropriate buffer layers between the diamond film and the substrate; and (3) by creating functionally gradient diamond-(titanium carbide, tungsten carbide, titanium nitride and aluminum nitride) composites. We have demonstrated that functionally gradient discontinuous buffer layers of titanium carbide, titanium nitride, aluminum nitride and tungsten carbide are able to control stress and graphitization in microcrystalline diamond thin films. This work on buffer layers and functionally gradient coatings should allow the development of more adherent crystalline diamond films for medical and tribological applications.     

新型金属-陶瓷覆层材料的研究

采用真空液相烧结技术。在钢基体表面制备三元硼化物硬质合金覆层。将三元硼化物硬质合金的优异性能赋予钢基体表面。获得耐磨抗蚀、界面结合强度高的新型硬质合金覆层材料。对三元硼化物硬质合金和钢基体的界面微观结构和界面区元素分布利用SEM-EDS进行分析。发现硬质合金覆层和钢基体之间形成了一个具有一定厚度的过渡层。合金元素浓度没有发生突变。两相之间形成了良好的冶金结合。并对覆层材料的显微硬度、抗弯强度与耐腐蚀性能做了研究。结果表明，硬质合金覆层材料具有较高的显微硬度、界面结合强度和优异的耐腐蚀性能。     

Core-shell ZrC/Ti2AlC reinforced composite coatings prepared by laser cladding on Zr-alloy substrates

Core-shell ZrC/Ti₂AlC reinforced intermetallic composite coatings were successfully prepared by laser cladding in-situ reaction using TiAl–TiC–Al powder preset on R60702 zirconium alloy surface. As-obtained coatings showed good metallurgical bonding with substrates. Composite coatings mainly contained dendritic ZrC/Ti₂AlC reinforced phase with core-shell structure and intermetallic matrix of Ti_xAl_y and Zr_xAl_y, with small amounts of Ti₃AlC. During laser pool solidification, TiC nucleated at boundary of primary precipitated ZrC dendrite. Al atoms then diffused into TiC outer layer during subsequent solidification process to finally form core-shell structure with ZrC as core and Ti₂AlC as outer layer. Ti₂AlC phase of shell structure improved physical performance between hard ZrC particles and matrix in terms of hardness and thermal expansion coefficient. The maximum hardness of cladding layer (848.8 HV) was 5-fold higher than that of zirconium alloy substrate. Also, no cracking was found inside the coatings or at the junction with substrates. In sum, these findings look promising for future applications of MAX phase composite coatings in nuclear power equipment.     

Microstructure and properties of Ni-WC gradient composite coating prepared by laser cladding

In this study, an Ni-based gradient composite coating reinforced with WC was prepared on a Q345R steel substrate by laser cladding. The Ni-WC composite coating was designed as a multilayer structure with gradient composition. The coating started with a layer of C276 alloy with 10 wt% WC on the substrate, and the subsequent layers were composed of Ni60 alloy with different WC contents (10, 30, and 50 wt% WC). The overall morphology, phase composition, and microstructure of the coatings were investigated. The microhardness and the wear properties of each layer of the coatings were also evaluated. The results showed that the gradient composition design was beneficial for reducing the cracking tendency. The coating was composed of an Ni-based matrix, WC, and multiple carbides and borides hard phases. With increasing WC content in the layers, the hard phases exhibited regional distribution characteristics. The WC reinforcement particles underwent different types of dissolution during the cladding process. From the surface to the substrate, the average microhardness of the coating was 1053.5 HV_0.2, 963.4 HV_0.2, 859.0 HV_0.2, 441.7 HV_0.2, and 260.5 HV_0.2. The wear tests revealed that the coefficient of friction and the wear loss values of the four layers were all lower than those of the substrate, demonstrating enhanced wear resistance.