等离子熔覆WC复合厚涂层特性研究

将Ni基合金和Ni包WC粉末混合均匀后事先涂覆在低碳钢基体上，通过非压缩弧等离子熔覆设备在低碳钢上制备Ni包WC复合厚涂层。涂层分为三种重量百分比Ni包WC粉末，分别为5％，10％，15％。应用X衍射（XRD）、光学显微镜（OM）、扫描电镜（SEM）、能谱仪（EDS）和显微硬度分析对涂层成分、微观结构和显微硬度进行分析。结果显示涂层和基体之间形成冶金结合，XRD显示主要的相是γ-Ni周溶体，以及Fe2B、Fe3B相和M23C6、M7C3相。发现等离子熔覆区的显微硬度随着Ni包WC粉末含量的增加而提高。     

激光熔覆Ni包WC复合涂层的组织、耐磨和耐蚀性分析及应用

对45钢基体进行激光熔覆Ni包WC金属陶瓷涂层强化处理,通过X射线衍射(XRD)、扫描电子显微镜-能谱分析(SEM-EDX)和透射电子显微镜(TEM),研究了激光熔履Ni包WC涂层的显微组织和物相组成,并采用摩擦磨损试验和电化学测试系统研究了Ni包WC涂层的摩擦磨损性能和耐蚀性能.结果表明,在激光熔覆Ni包WC金属陶瓷...     

激光重熔等离子喷涂NiCr-Cr3C2涂层微观结构和性能研究

利用扫描电镜(SEM)、能谱仪(EDS)、显微硬度计及金相分析软件,对等离子喷涂NiCr-Cr3C2涂层激光重熔前后的显微组织结构、硬度和孔隙率变化进行研究,并探讨不同扫描速度对激光重熔效果的影响.结果表明:利用激光重熔NiCr-Cr3C2陶瓷涂层,能够有效提高涂层的硬度和致密度,减少孔隙率;研究条件下1.5m/min的扫描速度时激光重熔效果最好.     

激光重熔高速电弧喷涂FeNiCrAl涂层的工艺优化

以外观形貌、孔隙率和显微硬度为评价指标,利用正交试验并结合极差分析法考察了激光功率、扫描速率和搭接步距这3个激光重熔工艺参数对高速电弧喷涂FeNiCrAl涂层重熔层的影响,得到优化工艺参数为:激光功率1 700 W,扫描速率10mm/s,搭接步距2.1 mm。结果表明,影响激光重熔最主要的参数是激光功率,随着激光功率的增大,重熔层的孔隙率先增大后减小,显微硬度显著增加。优化后所制重熔层的孔隙率为0.9%,显微硬度567.03 HV_(0.1),比喷涂层的显微硬度提高38.5%。重熔后,喷涂层的层状堆叠结构消失,产生了树枝晶和枝晶间组织。     

TiC添加量对等离子熔覆Ni60–WC复合涂层性能的影响

在45钢上通过等离子熔覆制备了WC?TiC?Ni涂层,对其物相、显微硬度和滑动摩擦磨损行为进行了分析.结果表明:熔覆层与基体材料之间为冶金结合,熔覆层表面无裂纹和气孔.TiWC2的形成使得熔覆层的显微硬度和耐磨性得到提高.当TiC的添加量为20％(质量分数)时,涂层的平均显微硬度高达1072.5 HV,较WC/Ni熔覆层高了128 HV,此时涂层的耐磨性最好.     

碳钢表面燃烧合成网络结构Cr_3C_2-WC陶瓷复合涂层的相组成与性能

利用燃烧合成技术,在普通碳钢表面原位自生Cr3C2-WC网络结构陶瓷复合涂层。通过X射线衍射仪、扫描电子显微镜、能谱仪和显微硬度计等测试手段对涂层中的网络结构陶瓷增强相的组织形貌、物相组成、化学成分及力学性能等进行了表征。结果表明:涂层由Cr3C2,WC,FeNi3,σ-FeCr和δ-CrNi等组成,Cr3C2-WC网络结构增强相由过饱和固溶体共晶析出。涂层与基体间的结合为冶金结合;表面涂层厚度约为2.0mm,显微硬度约为7.2GPa。制备的表面复合材料的硬度高于基体,改性效果明显。     

一水硬铝石等离子喷涂-激光重熔氧化铝陶瓷涂层的制备

以一水硬铝石为原料,利用等离子喷涂-激光重熔技术制备了氧化铝陶瓷涂层。扫描电子显微镜和X射线衍射分析表明：所制备涂层具有良好的显微结构。涂层显微硬度Hv可达12．14GPa。与一水硬铝石常规热分解直接生成α-Al2O3不同,涂层制备过程中存在过渡相γ-Al2O3,其原因在于等离子喷涂过程中一水硬铝石经历了高温高压及快速凝固过程。探讨了一水硬铝石热分解反应理论。     

激光重熔处理等离子喷涂陶瓷涂层的研究现状及展望

本文介绍了激光重熔等离子喷涂陶瓷涂层的研究进展,并对其进行了展望。激光重熔使等离子喷涂涂层致密性提高,涂层与基体的结合方式由机械结合为主改为冶金结合为主,层状组织变化为柱状组织;激光重熔使等离子喷涂涂层的热疲劳抗力、耐蚀性、耐磨性、抗高温氧化性等性能提高。指出了激光重熔等离子喷涂陶瓷涂层目前存在的问题,探讨了激光重熔等离子喷涂陶瓷涂层易产生裂纹,甚至发生涂层剥落等问题的原因,提出了激光重熔技术的研究方向。     

7×××系高强铝合金耐磨涂层的制备与性能

为了解决7×××系高强铝合金耐磨性差的问题,采用超音速火焰喷涂(HVOF)技术在7055铝合金基体表面分别制备了Cr2O3、Ni60和WC三种涂层,对涂层截面进行扫描电镜(SEM)观察及X射线衍射(XRD)物相分析,并测定了其显微硬度,借助摩擦磨损试验机和三维轮廓扫描仪对3种涂层的耐磨性进行比较,探究了它们的磨损机制。结果表明：在相同的热喷涂工艺条件下,3种涂层的耐磨性顺序为：WC> Ni60> Cr2O3。WC涂层的显微硬度达到1 213 HV,磨损率仅为3.33×10-4 mm3/(N·mm),耐磨性比7055铝合金基体提高了约12倍。该涂层中高硬度的WC硬质颗粒可以起到阻止磨粒磨损的作用,降低了磨粒的显微切削作用。采用超音速火焰喷涂技术可在7055系高强铝合金表面获得高硬度的耐磨涂层。     

激光功率对Fe基合金重熔热喷焊层组织和耐磨性的影响

利用金相显微镜和X射线衍射仪等分析手段,研究了Fe基合金热喷焊层在其他工艺参数相同的条件下,经不同激光功率重熔处理后组织结构的变化,并对其硬度和耐磨性进行了测定比较. 结果表明,Fe基合金热喷焊层的组织较粗大,经不同激光功率重熔处理后有不同程度的细化,激光功率越小,重熔热喷焊层组织越细小. Fe基合金重熔热喷焊层组织主要由g-(Fe,Ni)固溶体基体相和Cr7C3, Cr23C6及Cr2B等强化相组成,硬度和耐磨性较原始热喷焊层均有较大幅度提高,激光功率越大硬度和耐磨性越好,硬度提高约16%,耐磨性提高约55%.     

Novel Crystal Growth of In Situ WC in Selective Laser‐Melted W–C–Ni Ternary System

The bulk‐form in situ WC‐based cermets were prepared by selective laser melting of W–C–Ni ternary powder system. The in situ formed WC crystals generally had a unique triangular microstructure which was developed via a layer‐by‐layer growth mechanism by the multilayered stacking of (0001) basal planes of WC. An increase in the applied laser energy density, which was realized by increasing laser power or decreasing scan speed, resulted in the coarsening of in situ WC crystals in both side length and thickness, due to the elevated heat accumulation at the tips of the triangular WC crystals.     

超细WC／Co粉末及其烧结体的制备与表征

以水合肼为还原剂,于液相中制得超细we／co硬质合金包覆粉,后处理并进行低压烧结,制得力学性能良好的WC／Co硬质合金烧结体。考察了反应体系温度对反应时间的影响,搅拌速度对包覆率的影响,采用SEM、TEM、EDS等手段对包覆粉进行了表征;对比了不同规格、不同烧结方法对WC／Co烧结体力学性能的影响,采用金相、被散等照片对烧结体进行表征,并最终确定了制备WC／CO包覆粉及其烧结体的优化工艺条件。结果表明：此方法制得的WC／Co包覆粉纯度高,粒径均匀,低压烧结后所得烧结体力学性能良好。     

Carbide phases formed in WC–M (M = Fe/Ni/Cr) systems

The effect of composition in the formation of carbides in the WC–M (M = Fe/Ni/Cr) system has been studied. Three conventional compositions have been prepared with 10 wt.% of metallic binder. Fe as a metallic binder was first studied and its partial substitution by Ni and Cr was also investigated. A WC powder coated with a similar binder (Fe/Ni/Cr) amount was also investigated. The XRD results, after thermal treatment at 1400 °C, reveal that the substitution of half percent of the iron content by Ni stabilized the austenite Fe(γ) formation. The introduction of Cr in the binder composition induces the formation of Cr₂C carbide. With the decrease of Cr amount in the binder composition of the coated powder, Cr₂C carbide was not formed, but instead other carbide, M₆C, was detected. In order to eliminate this carbide a small excess of carbon (3.6 wt.%) was added to the coated powder. The results are discussed in terms of the phases formed, the binder composition and the final carbon content.     

Microstructure of laser cladded carbide reinforced Inconel 625 alloy for turbine blade application

Inconel 625 - WC metal matrix composite is a very promising material for high temperature applications. In this study, microstructure investigation and phase composition of a mixture between Inconel 625 and fine tungsten carbide (φ≈0.64 µm) was performed by means of XRD, SEM with EDS and TEM with EDS. Two powder mixtures were prepared: 20 wt% of WC and 30 wt% of WC and deposited on Inconel 625 substrate by laser cladding obtaining a crack and pore free material. The high temperature of the process resulted in partial dissolution of WC in Inconel 625 matrix. In sample containing 30 wt% of WC appearance of topologically close-packed (TCP) phases was observed at grain boundaries. WC, W2C, NbC, W₆C_2.54 and (W,Cr,Ni)₂₃C₆ were detected by XRD. Angular residual carbides and spherical oxide precipitates were visible in both types of samples. Processes occurring during laser action were explained.     

Ni-纳米WC复合镀层结构与性能研究

通过恒流电沉积制备Ni镀层和Ni-纳米WC复合镀层,利用扫描电镜和X射线衍射仪,并通过浸泡腐蚀实验和高温氧化实验,研究纳米WC颗粒对Ni镀层的微观形貌、物相结构、耐蚀性能和抗高温氧化性能的影响。结果表明,纳米WC颗粒使Ni镀层表面平整性明显改善,组织结构趋于完整且致密,镀层的耐蚀性能和抗高温氧化性能得到了提高;与Ni镀层相比,Ni-纳米WC复合镀层表面平整、结构致密,同等条件下的腐蚀速率和氧化增量均较低,表现出良好的耐蚀性能和抗高温氧化性能。     

粘结剂对超音速火焰喷涂碳化钨涂层磨粒磨损性能的影响

采用超音速火焰喷涂(HVOF)工艺在35钢基体上制备了WC-10Ni涂层和WC-12Co涂层,研究了镍、钴这两种粘结剂对WC涂层的显微硬度、摩擦系数和抗磨粒磨损性能的影响,采用扫描电子显微镜观察涂层磨损前后的表面形貌,探讨了WC涂层的磨粒磨损机理。结果表明,以HVOF方法制备的2种WC涂层均有较高的显微硬度,WC-10Ni涂层和WC-12Co涂层与SiC砂纸摩擦副之间的干摩擦系数相差不大。2种涂层在低载荷下均有较好的抗磨粒磨损性能,但在较高载荷下WC-12Co涂层的抗磨性明显优于WC-10Ni涂层。2种涂层的磨粒磨损形式主要为均匀磨耗磨损,磨损机理以微切削和微剥落为主。WC-12Co涂层的磨损表面损伤较轻微,综合性能优于WC-10Ni涂层。     

Lifetime prediction of WC-6Ni/SiC friction pair under seawater lubrication using an Inverse Gaussian model

The high reliability and extended life of seawater hydraulic components is dependent on the tribological properties of key friction pairs, more and more attention has been given to the performance degradation and lifetime of the friction pairs. In this paper, the wear process of Tungsten carbide (WC) with 6%wt of Ni (WC–6Ni)/SiC friction pair is studied through the tribological test under seawater lubrication. Considering the random effects and the complex wear mechanism of WC-6Ni/SiC, an efficient Inverse Gaussian (IG) process supported lifetime prediction model is established by coupling the multiple stresses under seawater lubrication, and the parameters in the proposed IG process model are derived. Two actual cases are used to validate the proposed method. The prediction model and experimental results show the high accuracy in time-varying lifetime prediction of WC-6Ni/SiC, which is of great significance to the evaluation of friction pair and the maintenance for seawater hydraulic components.     

Applicability of DLC and WC/C low friction coatings on Al2O3/TiCN mixed ceramic cutting tools for dry machining of hardened 52100 steel

The present work examines the applicability of DLC and WC/C low friction coatings on Al₂O₃/TiCN based mixed ceramic cutting tools for the dry and hard turning of AISI 52100 steel (62 HRC). The characterization of coated tools reveals that the coatings retain very low values of surface roughness, whereas the DLC coating exhibits much higher microhardness when compared to the WC/C coating. On the other hand, the WC/C coating exhibit a coarse surface morphology virtually due to the tungsten doping. Later, continuous turning tests were executed with the help of coated and uncoated cutting tools under dry cutting conditions, and their performance was investigated in terms of machining forces, cutting temperature and tool wear. Coating delamination by flaking and peeling is quite prominent in the case of both the coatings; however, it is less severe for the WC/C coated tool. The coatings help to reduce machining forces, cutting temperatures and tool wear, but the performance of coated tools converge towards uncoated tool as the cutting speed, and feed rate is increased. Both the coatings prevent the development of cracks near the cutting edge with WC/C coating exhibiting superior wear behavior basically due to its multilayered structure and better thermal stability. Moreover, the tested low friction coatings don't serve as thermal barriers and only the lubrication generated due to graphitization at the chip-tool interface is mostly responsible for the improved machining performance.     

The effect of tungsten buffer layer on the stability of diamond with tungsten carbide–cobalt nanocomposite powder during spark plasma sintering

WC–Co nanocomposite powder produced by spray pyrolysis–continuous reduction and carbonization technology, diamond coated with tungsten (W) by vacuum vapor deposition and uncoated diamond were used in this study. This work adopted the spark plasma sintering (SPS) process to prepare diamond-enhanced ultrafine WC–Co cemented carbide composite material. The effects of W buffer on the stability of diamond with WC–Co nanocomposite powder during SPS were investigated. Results showed that the uncoated diamond was mechanically embedded in WC–Co cemented carbide matrix, while the diamond coated with tungsten was combined chemically with WC–Co cemented carbide matrix. Moreover, there was a transitional layer between the diamond and the matrix which could improve the thermal stability of the diamond, prevent carbon atom of the diamond from dissolving in Co phase and increase the bonding strength of the interface between the diamond and the matrix.     

Electrochemical Behavior of TiCN–Ni-Based Cermets

The electrochemical behavior of TiCN–20 wt% Ni cermets containing different secondary carbides (10 wt% WC, NbC, TaC, and HfC) was investigated in freely aerated 0.2 mol/L sulfuric acid. A comparison has also been made with polarization behavior of pure Ni. All the materials (except HfC-containing cermet) exhibited active–passive polarization behavior, characterized by two passive regions. The first passive region, obtained on polarizing past the zero current potential, was attributed to passive film formation due to TiCN, while the second passive film is presumably due to the presence of a Ni binder phase. The passivation behavior in the case of cermets containing various secondary carbides (WC, TaC, and NbC) was similar to baseline TiCN–20Ni cermets, while poor passivation behavior was observed in the case of TiCN–20Ni–10HfC. Efforts have been made to correlate the passivation behavior with the microstructural characteristics of sintered cermets.