Microstructure and properties of WC reinforced Ni-based composite coatings with Y2O3 addition on titanium alloy by laser cladding

ABSTRACT

In this study, WC reinforced Ni-based composite coatings with Y₂O₃ addition were deposited on Ti-6Al-4V titanium substrate by laser cladding. The phases, microstructure, microhardness and wear resistance of the composite coatings were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, microhardness tester and wear tester. The results showed that good metallurgical bonding was achieved between the composite coatings and substrate. The phases mainly were γ-Ni, TiC, TiB₂, Ni₃B, M₂₃C₆ and WC. Most of the WC was dissolved in small pieces of WC during the laser cladding process. The microhardness of the composite coatings was about 3 times that of the titanium substrate and the wear resistance of the composite coatings had a significant increase.     

Effect of rare earth on microstructure and carbides in WC-Fe composite coating

WC-Fe composite coatings were prepared on IC45/080A47 steel substrates by argon arc cladding technique. Minute amounts of La were added into the coating, and the microstructure was investigated to find the relation to rare earth. Results show that RE does not change the categories of phases, and the main components remain α-Fe, Fe₃W₃C, WC and W₂C. However, the distribution of carbide particles is optimised. It reduces the agglomeration and bridging in the cladding layer's structure, makes the particles distribute homogeneously and restrains the dissolution of WC and the formation of fishbone shaped dendritic carbides. It promotes the formation of granular carbide and refines grains. It also reserves the WC particles in the composite coating and improves the average hardness and wear resistance.     

Effect of infiltration parameters on composition of W-ZrC composites produced by displacive compensation of porosity (DCP) method

In this study, the effect of infiltration parameters on composition of W-ZrC composites produced by displacive compensation of porosity (DCP) method was investigated. For this purpose, a porous tungsten carbide preform was prepared by cold isostatic pressing (CIP) of tungsten carbide powder and polyvinyl alcohol (PVA). The porous preform was debinded for 4 h at 400 °C and sintered for 4 h at 1400 °C. The sintered preform was then infiltrated by molten Zr₂Cu at 1300 °C and 1200 °C for 1, 3, 5 and 7 h. Scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometer (EDS) and X-ray diffraction (XRD) were used to study the cross section of infiltrated specimens. The results indicated that the amount of tungsten and zirconium carbide phases increased by increasing the infiltration temperature, whereas the effect of infiltration time on composition of W-ZrC composite was negligible.     

Model single point abrasion experiments on WC/Co hardmetals

WC based hardmetals are widely used in applications where abrasion resistance is important.This paper describes the utility of scratch tests as model single point abrasion tests to evaluate the response of WC/Co hardmetals to the type of conditions that will occur in abrasion. The different types of experiments were single and multiple pass tests, and multiple pass tests in corrosive media.The resultant scratches were observed by stepwise SEM imaging, stereographic image correlation and 3D reconstruction, and EBSD analysis.It was found that many of the features observed in the model tests paralleled those seen in other abrasive tests on WC/Co materials such as build up of plastic damage in WC grains, fracture and fragmentation of WC grains, deformation of the Co binder phase and re-embedment of WC grains in the surface layers of the material. For tests in the presence of corrosive media, the binder phase was removed early in the sequence of scratches, leading to breakdown of the structure of the material.Stereo reconstruction was shown to be a valuable way of visualising and measuring the physical dimensions of scratches, providing a future route for the quantification of damage in these model experiments.     

镍基合金+WC激光熔覆层的显微组织形成机理及控制

采用光学显微镜、X射线衍射仪、扫描电子显微镜、能谱分析等手段对镍基合金+WC熔覆粉末颗粒的颗粒种类、颗粒粒径、不同种类颗粒的分布及镍基合金+WC激光熔覆层内各种组织的不均匀分布进行了研究。根据热平衡原理建立了熔覆材料颗粒半径、激光束功率密度和熔覆材料颗粒加热温度之间的定量关系式,提出通过控制各种熔覆材料颗粒大小来实现设计与控制送粉激光熔覆层的显微组织,并以WC与N i基自熔合金混合粉料为熔覆材料,对获得的熔覆层的显微组织进行分析,证明了所提出的熔覆层显微组织的设计与控制方法的可行性与实用性。     

Ni基合金+WC激光熔覆层再加热时的显微组织变化特性

采用Ni基自熔合金+块状WC混合粉末进行送粉激光熔覆并获得熔覆层,对熔覆层在不同温度下加热后空冷至室温,观察相应熔覆层的显微组织变化,结果表明：Ni基自熔合金+WC送粉激光熔覆层不适合在500℃～900℃再加热处理,再此温度区间对熔覆层再加热会导致块状WC出现裂纹。Ni基自熔合金基体的显微组织在700℃以上开始不稳定,发生形态和显微组织结构的变化。熔覆层中的块状WC加热至900℃以上时裂纹会被自行焊合,温度继续升高,块状WC会发生离散,分化成细小的WC颗粒,产生这种现象的根本原因是块状WC具有先天的超细纤维、颗粒混合结构。     

In situ spectroelectrochemical measurements during the electro-oxidation of ethanol on WC-supported Pt-black. Part II: Monitoring of catalyst aging by in situ Fourier transform infrared spectroscopy

As a continuation of a project on the spectroelectrochemical analysis of long-term behaviour of WC-supported Pt electrocatalysts (for SFG results, see part I: [1]), in this paper we report in situ FT-IR spectroscopy experiments, carried out during prolonged electro-oxidation of ethanol on Pt-black. From the analytical point of view, as expected, FT-IR spectra showed the presence of adsorbed acetic acid and ethanol, in addition to the well-known, dominant species: linearly adsorbed CO (2044-2063 cm⁻¹) and solution-phase CO₂ (2345 cm⁻¹). As far as quantitative spectroscopic results are concerned, a notable sensitivity of the interfacial chemistry to catalyst aging could be highlighted by this approach. The spectra recorded in three subsequent series of potential-cycling experiments showed a clear-cut dependence of spectral patterns and peak intensities, on the applied potential and on the oxidation duration. Qualitative spectral changes seem to suggest - coherently with in situ SFG results obtained with the same system [1] - that electrocatalyst aging correlates with a higher surface coverage with ethanol as compared with acetic acid. Quantitative analysis, based on fitting with Lorentzian lineshapes, yields information that can be used as a molecular-level diagnostic of the modification of the catalyst-adsorbate structure.     

Thermal spray coating on conductor rolls in electroplating line

In electroplating lines,many conductor rolls are installed in electroplating bath.Typical electroplatings are tin plating(ETL) and zinc plating(EGL),and from required product qualities,a vertical cell for the former and a horizontal cell for the latter is often used.Generally,chrome plating or WC cermet thermal spray coating is applied to stainless steel conductor roll in ETL for prolonging service life by improvement of wear resistance and corrosion resistance.On the other hand,Hastelloy type alloy subs...     

WCp/Cr-Ni钢基局部增强复合材料防暴性能的研究

为厂获得具有综合抗暴力破坏特性的新型金库增强材料，进行了基体化学成分的设计，采用铸造法制作了碳化钨颗粒WCp／Cr—Ni钢基局部增强复合材料。对其防暴性能(抗冲击、抗O2—C2H2焰切割、抗钻削)进行了测试，并用SEM、EPMA、XRD等仪器对复合材料中碳化钨颗粒的分布、界面、相组成等进行了观察分析，探讨了具备防暴性能的机理。结果认为，该材料具有比较良好的综合防暴特性，有希望成为新型的金库增强材料。     

45钢表面激光熔覆WC／Co金属陶瓷

研究了45钢表面WC／Co金属陶瓷激光熔覆层的组织、界面特征及其形成机制,分析了激光熔覆层中涂层元素和硬度的分布特征。结果表明,激光熔覆使WC／Co等离子喷涂层的片层状组织特征消除,形成了连续致密的熔覆层;由于涂层中不同部位的成分。温度分布及冷速不同使初生相呈树枝状、多边形块状、花瓣状、条状及颗粒状等几种形态;实现了涂层与基体间的冶金结合,结合带宽度约3-5μp;涂层硬度达1794HV0.1。