Abrasive performance of the chromium carbide reinforced Ni3Al matrix composite cladding in different depth

 The Microstructure and room-temperature abrasive wear resistance of chromium carbide reinforced Ni3Al matrix composite cladding in different depth on nickel base alloy were investigated. The results showed that there is a great difference in microstructure and wear resistance of the Ni3Al matrix composite in different depth. Three kinds of tests, designed for different load and abrasive’ size, were utilized to understand the wear behaviour of this material. Under all three wear conditions, the abrasion resistance of the composite cladding in the depth of 6mm, namely NC-M2, was much higher than that of the composite cladding in the depth of 2mm, namely NC-M1. In addition, the wear-resistant advantage of NC-M2 was more obvious when the size of the abrasive was small. The relative wear resistance of NC-M2 increased from 1.63 times to 2.05 times when the size of the abrasive decreased from 180μm to 50μm. The microstructure of the composite cladding showed that the size of chromium carbide particles, which was mainly influenced by cooling rate of melting pool, as a function of distance from the interface between the coating and substrate was gradual. The chromium carbide particles near the interface were finer than that away from interface, which was the main reason for the different wear resistance of the composite cladding in different depth.     

Structure and Mechanical Properties of NiPNano Al2O3 Composite Coatings Synthesized by Electroless Plating

NiPnano Al2O3 composite coatings were deposited by electroless plating, and their microstructures were observed by SEM (scanning electron microscope). The microhardness and the wear resistance of the NiPnano Al2O3 composite coatings were measured using microhardness tester and blockonring tribometer, respectively, and the comparison with those of NiP coatings or NiPmicro Al2O3 coating was given. The influences of aging temperature on their hardness and wear resistance were analyzed. The results showed that the nano Al2O3 particles were distributed uniformly in the NiPAl2O3 coatings. Among three kinds of NiP based coatings, the hardness and wear resistance of NiPnano Al2O3 coatings were largest, and the maximum values could be obtained at 400 ℃. This indicated that the precipitation of nano Al2O3 particles would improve the hardness and wear resistance of the NiP coatings.     

Influence of laser re-melting and vacuum heat treatment on plasma-sprayed FeCoCrNiAl alloy coatings

FeCoCrNiAl high entropy alloy coatings were prepared by supersonic air-plasma spraying.The coatings were post-treated by vacuum heat treatment at 600 and 900°C,and laser re-melting with 300 W,respectively,to study the influence of different treatments on the structure and properties of the coatings.The phase constitution,microstructure and microhardness of the coatings after treatments were investigated using X-ray diffraction,scanning electron microscopy and energy dispersive spectrometry.Results showed that the as-sprayed coatings consisted of pure metal and Fe-Cr.The AlNi_3 phase was obtained after the vacuum heat treatment process.A body-centered cubic structure with less AlNi_3 could be found in the coating after the laser re-melting process.The average hardness values of the as-sprayed coating and the coatings with two different temperature vacuum heat treatments and with laser re-melting were 177,227,266 and 682 HV,respectively.This suggests that the vacuum heat treatment promoted the alloying process of the coatings,and contributed to the enhancement of the coating wear resistance.The laser re-melted coating showed the best wear resistance.     

Influence of Lanthanum on Tribological Properties and Microstructure of Laser Clad B ＋ Fe ＋ Si Composite Coatings

The effects of rare earth ferrosilicon on the microstructure and anti-wear properties of laser-clad Fe-based alloy coating were investigated. The composition of Fe, B4C and rare earth ferrosillcon powders with different contents of lanthanum were clad onto a 45 # carbon steel substrate. Microstructural features, chemical compositions, phase structure,hardness, friction and wear properties by scanning electron microscopy (SEM), X-ray photoelectron microscopy (XPS),hardness tester, block-on-ring friction and wear tester of the clad coating were determined. Experimental results show that the friction coefficient of the clad coating doped with rare earth ferrosilicon is reduced while the wear resistance of clad coating doped with rare earth ferrosilicon is enhanced. When the content of lanthanum increases to 1.92%, the clad coating shows the best anti-wear ability, and as the content of lanthanum exceeds 1.92%, the wear weight loss increases quickly. The rare earth ferrosilicon to be doped in the clad coatings helps to disperse the boride phase (Fe2B, FeB, B4C)particles and refine the grain of boride phase. The enhancement of clad coating‘s wear resistance is due to the existence of dispersed boride phases.     

Distribution Characteristics and Reinforcing Behavior of (Ti,Nb)C Reinforced Particle in the Coating Fabricated by Laser Rapid Cladding

(Ti,Nb)C reinforced Fe-based laser coatings were prepared with normal and high scanning velocities of the laser beam.The distribution characteristics of reinforced particles in the coatings were investigated.The mechanical properties of coatings were tested.The results showed that the morphologies of the microstructure and the reinforced particle changed dramatically at high solidification rate due to rapid laser processing compared with that prepared by normal processing.Two kinds of particles were observed in the coating.One was(Ti,Nb)C multiple carbide particle with the size of micron and sub-micron scales,in which a mass of dislocations were found.Another was nano-sized particle includingα-Fe and(Ti,Nb)C obtained by rapid solidification.The microstructure of the coatings was highly refined and a large number of twin crystals were found in matrix.The results of mechanical properties test revealed that the wear resistance of the coating was improved by rapid laser processing,compared with that of the coating prepared with normal speeds.The above-mentioned conclusion indicated that rapid laser cladding can promote not only the processing efficiency but also the mechanical properties of the coating.     

Characteristics of Stellite 6 Deposited by Supersonic Laser Deposition Under Optimized Parameters

Stellite 6 powders were deposited on low carbon steel using SLD (supersonic laser deposition) under optimized parameters. The structure, line scan of elements and porosity of coating were examined and analyzed using SEM (scanning electron microscope), OM (optical microscope) and XRD (X-ray diffraction). The adhesion strength between coating and substrate was tested by PAT-ADHESION/TENSILE and E900STM adhesive. The results showed the deposition characteristics of optimized coating with N2 at a pressure of 3.0 MPa, a temperature of 450 ℃ and a laser power of 1.5 kW were compared with those of Stellite 6 coating deposited by the HVOF (high velocity oxygen fuel).     

Tribological Properties of Laser Cladding Fe-B Layer Containing Lanthanum

In order to study the influence ot rare earth(RE) elements on the tribological properties of laser melt cladding Fe-B layer, laser melt cladding experiment was performed using Fe, B4C, FeSiRE powder on steel 45 substrate. Systematic wear tests were done for laser cladding layer containing different content of RE on HQ-1 wear machine. The results show that wear resistance of laser melt cladding layer containing a certain amount of RE elements is remarkably improved, when the content of RE exceeds the optimum amount,     

Development of New WearResistant Surface Coating at Elevated Temperature

Because of good oxidation resistance at high temperature and excellent mechanical properties of Ni3Al and high hot hardness, and good oxidation resistance of chromium carbide, chromium carbide particle reinforced Ni3Al matrix composite would possess excellent wear resistance at elevated temperature. Cr3C2NiAlNi welding wire was produced by pressureless sintering process in vacuum. When the welding wire was welded on the surface of carbon steel, under the action of the physical heat of arc, NiAl reacted with nickel to form Ni3Al and carbide particle reinforced Ni3Al matrix composite was formed on the welding layers. Cr3C2 was dissolved during welding and dispersed Cr7C3 was formed, which strengthened the Ni3Al matrix significantly. The Cr7C3Ni3Al interface was broadened, and a zone of interdiffusion and a new phase M23C6 were formed, indicating that a good bond has been formed. The hardness of Cr7C3/Ni3Al composite at room and elevated temperatures is much higher than that of stellite alloys. In addition, Cr7C3/Ni3Al composite possesses better high temperature oxidation resistance than stellite 12 alloy. So Cr7C3/ Ni3Al composite can become an attractive potential candidate for elevated temperature wearresistant surface material.     

Micro-Crystalline Coatings of Co-Cr Dispersed with Y2O3 Deposited by Series Electro-Pulse Discharge

A new technique-series electro-pulse discharge (SEPD)-was developed as a kind of surface coating process. In this technique, both positive and negative poles of a pulse power were used as the depositing electrodes with the substrate alloy as an induction electrode. Micro-crystalline Co-Cr and Co-Cr dispersed with Y2O3 coatings were deposited on Fe-18Cr-SNi stainless steel surface by using Co30Cr alloy as the depositing electrodes. Oxidation at 950℃ in ambient air shows that these coatings greatly improve the oxidation resistance of the steel. The addition of dispersed Y2O3 nano-particles into the alloy coatings was found to further reduce the scaling rate and enhance the adhesion of oxide scales.     

通过等离子渗碳/CrN覆层改性处理提高Ti-6Al-4V合金的耐磨性和抗疲劳特性

In this study, a newly developed duplex coating method incorporating plasma carhurization and CrN coating was applied to Ti-6AI-4V and its effects on the wear resistance and fatigue life were investigated. The carburized layer with approximately150μm in depth and CrN coating film with 7. 5 μm in thickness were fomled after duplex coating. Hard carbide particles such as TiC And V4C3 were formed in the carburized layer. XRD diffraction pattern analysis revealed that CrN film had predominant [111] and [200] textures. The hardness (Hv) was significantly improved up to ahout 1960 after duplex coating while the hardness value of original Ti-6Al-4V was 402. The threshold load for the modification and/or failure of CrN coating was measured to be 32 N using the acoustic emission technique. The wear resistance and fatigue life of duplex coated Ti-6Al-4V improved significantly compared to those of un-treated specimen. The enhanced wear resistance can be attributed to the excellent adhesion and improved hardness of CrN coating film for the duplex coated Ti-6Al-4V. The initiation of fatigue cracks is likely to be retarded by the presence of hard and strong layers on the surface, resulting in the enhanced fatigue life.     

石墨烯对激光熔覆镍基碳化钨涂层组织及性能影响

采用激光熔覆技术在Q235钢基体上制备Ni60A-30%WC-x%石墨烯(质量分数, x=0.0, 0.1, 0.3, 0.5)涂层, 研究石墨烯对激光熔覆镍基碳化钨涂层组织与性能的影响。结果表明, 涂层物相主要由具有γ相结构的Ni-Cr-Fe固溶体、WC、W₂C、Cr₇C₃、Cr₂₃C₆、B₄C等组成; 石墨烯改善了激光熔覆镍基碳化钨涂层的组织, 提高了涂层的硬度和抗摩擦磨损性能; 当石墨烯质量分数为0.3%时, 得到了析出相分布均匀且细小的组织, 涂层具有高硬度、良好的抗裂纹扩展能力和耐磨性。     

高锰钢表面激光熔覆 Fe-WC 复合涂层的组织与性能

采用激光熔覆技术在高锰钢基体上制备了不同WC含量的Fe-WC复合熔覆层,研究了WC添加量对熔覆层组织和性能的影响。试验结果表明,不同WC含量的Fe-WC熔覆层均含有马氏体、M7C3碳化物和未熔WC颗粒,当加入20wt.%的WC时,熔覆层中出现了残余奥氏体,共晶碳化物呈鱼骨状沿晶界析出。Fe-WC熔覆层的硬度和耐磨性随着WC添加量的增多而增大,熔覆层中WC颗粒减小熔覆层基体与对磨副的接触面积,合金基体固定和支撑WC颗粒避免其剥落,二者协同作用使得熔覆层耐磨性增加。     

TC4钛合金表面激光熔覆Ni包WC复合涂层研究

为了提高钛合金的耐磨性能及使用性能,采用激光熔覆法在TC4钛合金基体上制备了Ni与WC混合粉末涂层,研究了不同WC添加量对熔覆层的物相组成、显微组织、硬度及耐磨性能的影响。结果表明,三组不同的熔覆材料经过激光熔覆后,都可以使材料表面硬度和耐磨性能较基材大幅度增加。但是随着WC含量的增加,熔覆层均匀性降低,出现小颗粒的WC团,并且组织开始多样化,且硬度分布均匀性也有所下降。     

激光熔覆涂层的浆体磨损特性及其应用研究

采用激光熔覆技术在４５钢试样表面获得镍基合金和ＷＣ颗粒增强的镍基合金复合材料涂层。研究了激光涂层工艺、熔覆层的组织结构和水平－煤－石英砂浆体的磨损特性,并将研究成果成功地应用于矿用渣浆泵平衡盘等零件。     

激光功率对碟阀表面熔覆Ni 基合金涂层性能的影响

采用半导体激光器在2205双相不锈钢表面激光熔覆Ni基合金涂层.借助扫描电镜、电化学综合测试仪和硬度测试仪等,探讨了激光功率对涂层稀释率、微观组织、耐腐蚀性能及硬度的影响.结果表明:激光功率越大,涂层稀释率越大,熔覆层与基体元素发生更多的对流扩散;熔覆层的耐腐蚀性能随激光功率的增加而降低,当激光功率为2.7 kW时,熔覆层的自腐蚀电位最低,为-0.46 mV,腐蚀电流最小,为3.47×10-5 A/cm2. 硬度测试实验表明,激光熔覆Ni基合金涂层硬度最高达680 HV,约为基体硬度的2.5倍.      

一种基于 Ni60 的激光熔覆耐磨合金粉末设计

针对Ni60合金粉末进行了成分设计优化,通过添加WC提高耐磨性,调整B和Si元素以及WC含量控制熔覆层的开裂敏感性,并进行了工艺验证,形成了激光熔覆专用耐磨合金粉末。结果表明:设计的新粉末经激光处理后,可获得无明显裂纹而微观裂纹少的较高质量熔覆层,熔覆层的开裂敏感性减小,耐磨性明显提高。     

激光熔覆WC/Ni60B复合涂层在水润滑滑动摩擦环境下的磨损特性

采用激光熔覆技术制备了Ni60B镍基合金涂层以及微米WC、纳米WC和微-纳米WC颗粒增强的Ni60B基复合涂层（分别称为WCm、WCn和WCmn复合涂层）.对制备涂层在Amsler200磨损试验机上进行了不同载荷和滑动距离的水润滑滑动磨损试验.结果表明:WC颗粒的加入显著提高了Ni60B涂层的耐磨性.WCm复合涂层和纳米WCn复合涂层的耐磨性差别不大,但磨损形貌不同.涂层在水润滑环境下的磨损量均远远低于干滑动摩擦,其原因是水膜的支撑或隔离作用降低了涂层与磨轮之间的接触应力,水的冷却作用减少了摩擦热引起的温度升高,降低了涂层摩擦表面的温升和热软化.水润滑摩损条件下,WCm和WCn复合涂层中过饱和W元素发生扩散和聚集.      

紫铜上激光熔覆镍基自熔合金组织和性能研究

采用万瓦横流CO2激光器在紫铜表面熔覆镍基自熔合金熔敷层,并采用SEM、XRD、OM和显微维氏硬度计进行组织结构和硬度分析。结果表明:在紫铜表面完全可采用激光熔覆的方法制备镍基自熔合金的熔覆层,熔覆层与铜基体形成冶金结合,组织致密、晶粒细小、无裂纹、孔隙夹杂等缺陷,熔敷层内具有等轴晶、树枝晶及胞状晶等不同结构,并有WC、W2C、Ni3B等强化相颗粒。同时,与采用超音速火焰喷涂(HVAF)涂层进行对比,结果表明激光熔覆层硬度虽然低于喷涂涂层,但磨擦系数小,耐磨损性能有明显的提高。     

激光熔覆铁基涂层工艺参数的研究

以激光熔覆铁基涂层为研究对象,在MM-P2屏显式摩擦磨损试验机上进行摩擦磨损对比实验,分析了不同工艺参数下熔覆层形貌及熔覆涂层后磨损量的变化关系.结果表明:熔覆涂层后的表面硬度均在62HRC以上,远高于基体的硬度;熔覆层的形貌和质量主要影响因素是扫描速度,激光功率次之,并在此基础上采用能量密度进行表征,能量密度为60 J/mm2左右时的耐磨性最好,其最佳组合工艺参数为激光功率3.2 kW左右、扫描速度300 mm/min左右.激光功率过高,扫描速度过快都会导致熔覆层耐磨性能下降.      

Ceramic-Metal Composite Coating by Laser Cladding

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