Structural characterization and adhesion appraisal of TiN and TiCN coatings deposited by CAE-PVD technique on a new carbide composite cutting tool

A new composite matrix was developed for a cutting tool based on tungsten carbide ligated with cobalt (WC-Co) using sintering technique. The admixtures of niobium carbide, tantalum carbide, and titanium carbide with the WC-Co matrix aim to inhibit the grain growth of WC and to promote covalent bonding at the interface. The modified WC-Co tools were coated with titanium nitride and titanium carbonitride layers by CAE-PVD technique. To substantiate the performances of the new coating-substrate systems, we have performed X-ray diffraction, atomic force microscopy, and scratch test measurements to estimate: phase content, average crystallite size, average texture coefficient, residual stress level, coating thickness, average roughness, square mean root, fractal dimension, cohesive adhesion, and adhesive adhesion. The results enable the in-depth understanding of the coating growth mechanisms and provide an objective evaluation of the coatings adhesion to the new cutting tools matrix. The results provide evidence to support the potential of TiN and TiCN coatings to enhance the working performances of the composite WC-Co cutting tools and to differentiate their properties. TiCN coating is shown to be superior to TiN coating in terms of adhesion and thus represents a better alternative for coating the modified WC-Co composite matrix.     

阴极电弧离子镀ZrN梯度膜和Zr/ZrN多层膜的腐蚀特性

采用阴极电弧离子镀技术在1Cr13不锈钢表面制备了ZrN梯度层和Zr/ZrN多层膜,并用电化学腐蚀方法和中性盐雾法检测了1Cr13基体、ZrN梯度层和Zr/ZrN多层膜的耐腐蚀性能.结果表明:Zr/ZrN多层膜和ZrN梯度层均能提高1Cr13基体的抗腐蚀能力,而Zr/ZrN多层膜的效果更明显:镀层的内部缺陷(如微孔)和液滴导致薄膜发生孔蚀、隙缝腐蚀和电偶腐蚀;镀层保护的实质是物理屏障作用,细化晶粒、减少膜层中的液滴及针孔等缺陷能显著提高薄膜的抗腐蚀性能.     

Wear behaviors of TiN/TiCN/DLC composite coatings in different environments

Diamond like carbon (DLC) coatings have high wear resistance and low coefficient of friction and its features are being tried to be further developed. We deposited TiN/TiCN/DLC composite coatings on inconel substrates with closed field unbalanced magnetron sputtering system to improve the features of the conventional DLC coatings. Structural, chemical and bond types of the coating were obtained with the XRD, SEM, EDS and XPS analyses. Wear behaviors of the coatings were determined in atmosphere, distillated water and commercial oil conditions under low (2 N) and high (10 N) constant load values with using pin-on-disc tribo-test system. The wear results demonstrated that using the TiN/TiCN layers with the DLC coatings increased the load carrying capacity, decreased the CoF, and wear rates at the high load values.     

Wear and friction behavior of CrTiN/TiCN and CrTiN/CrCN multilayer composite coatings

Multi-layer CrTiN/CrCN and CrTiN/TiCN coatings were deposited on 2379 and SLD steels by cathodic arc physical vapor deposition (arc-PVD) in different thicknesses. Coatings are mechanically, physically, and chemically characterized by nanoindentation, optical microscope, atomic force microscope (AFM), and scanning electron microscope/energy-dispersive X-ray (SEM/EDX) analyses. The crystal structure of the coatings was investigated by X-ray diffraction (XRD) analysis. Wear and friction characterizations were performed via reciprocating tribometer tests under 2.4 and 3.0 GPa Hertzian contact pressures at the unlubricated conditions. Results showed that CrTiN/CrCN coatings demonstrated excellent wear resistance and friction coefficient (COF) at elevated contact pressures both on 2379 and SLD steels.     

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.     

TiCN and metallic coatings for corrosion protection of separator plates in MCFCs

Stainless steel 304 substrates were coated with different materials in order to find a suitable coating material for corrosion protection of separator plates in molten-carbonate fuel cells (MCFCs). Five titanium carbonitride coatings differing in composition and morphology and a titanium monoxide coating were deposited with chemical vapour deposition techniques. Also double-layer coatings of TiN/Au and TiN/Ni were prepared. The coatings were tested on their corrosion protection of separator plates in four different environments: under MCFC-cathode or anode gas, at load or at open circuit conditions. The corrosion behaviour was characterized using cyclic voltammetry. Corrosion rates were determined with electrochemical methods and cross-section analyses of corrosion layers. Titanium nitride coatings showed the best corrosion protection. The titanium carbide and titanium monoxide coating showed respectively less and no protection. The thin gold and Ni-coatings were unstable. Under cathode gas, the most important corrosion protection is given by keeping the cell at load, and then a titanium nitride coating might provide lifetime protection. Under anode gas, corrosion is most severe at load conditions. A titanium nitride coating also gives corrosion protection, but not enough for lifetime protection.     

The crystallization behaviours of reactive-plasma-sprayed TiCN coatings with different Ti/graphite powder ratios

TiCN coatings were reactive plasma sprayed with different Ti/graphite powder ratios. Their crystallization behaviours were investigated. The results showed that the TiN coating consisted of TiN and TiN_0.3O phases. With the decrease in the Ti/graphite ratios, the phases in the coatings changed from TiC_0.7N_0.3+TiC_0.3N_0.7+amorphous (Ti:graphite = (6-10):1) to TiC_0.3N_0.7 + TiC + amorphous (Ti:graphite = 4:1). The surface of the TiN coating exhibited the columnar crystals. With the decrease in the Ti/graphite ratios, the columnar crystals gradually skewed towards the surface. The cross-section crystalline morphologies of all the coatings exhibited the layer-layer columnar crystals with better bonding interfaces between the layers. The micro-hardness of the sprayed TiN coating was 1000 HV_0.1. The micro-hardness of the TiCN coatings increased with the decrease in the Ti/graphite ratios. The maximum microhardness (1315 HV_0.1) was observed at a Ti/graphite ratio of 4:1, approximately 30% higher than that of the TiN coating. The increase in the micro-hardness was correlated with the phase composition and crystalline morphologies.     

Evolution of a metastable thin film with high-hardness wear resistance for advanced cutting tool application

The structure and elastic properties of rocksalt and wurtzite Ti–Al–N ternary solid solutions were investigated using first principles calculations. We also performed an experimental evaluation using the sputtering method to obtain the reliability. The phase transition of (Ti_1−xAl_x)N solid solutions was occurred at x = 0.5–0.75 for both calculations and experimental results. The bulk modulus of rocksalt and wurtzite solid solutions decreases with increasing Al content. On the other hand, shear moduli and Young's moduli gradually increase with Al content only in rocksalt solid solutions. The theoretical and experimental results indicate that the overall mechanical properties of rocksalt solid solutions are superior to those of wurtzite solid solutions. Therefore, controlling the crystal structure of the Ti–Al–N ternary metastable system was crucial for optimizing the material properties.     

荒料开板工具存在的问题及新型工具的研制

首先比较了几种现有荒料开板工具的性能特点,分别计算了它们的锯切成本,从而分析了现有工具存在的问题.由此提出了将金刚石链锯应用于荒料开板的设想,并分析了这种新型荒料开板工具可能潜在的优势.     

PDC刀具设计要素的选择原则

随着现代科学技术的迅猛发展,各种新材料及难加工材料层出不穷,PDC刀具以其特有的性能优势适应了现代加工制造业的发展需求,成为未来刀具技术发展的趋势,然而我国PDC刀具的设计制造与国外先进水平还存在很大的差距,文章对PDC刀具材料、刀体、主偏角、副偏角、后角、前角、刃倾角、刀尖圆弧、刃带等要素的作用进行了分析,论述了各要素的选择原则,为PDC刀具的生产设计提供了一定的参考依据.     

Characterization and modification of fillers for paints and coatings

This paper highlights the possibility of inverse gas chromatography for the surface characterization of common fillers (CaCO₃, talc, SiO₂,) for paints and coatings. Divided solids are described, on the one hand, by the dispersive component of their surface energy and, on the other, by a specific parameter indicating their acid-base interaction potential. The role of the surface morphology at a molecular level is also examined. It is demonstrated that steric effects play an important role in the adsorption of probes on lamellar solids like talc. The consequences of surface treatments as well as examples of practical applications are also reported.     

Preparation and properties of thermosetting powder/graphene oxide coatings for anticorrosion application

The goal of this research was to simplify the preparation process of graphene-contained powder coatings for metal anticorrosion. To do this, thermosetting powder/graphene oxide (TP@GO) composites were prepared via a facile planetary ball-milling technique and were painted onto tinplates by electrostatic spraying. After immersion in a 3.5 wt % NaCl solution for 9 days, potentiodynamic polarization curves revealed superior anticorrosion performance for the 1.5 wt % graphene oxide coating (TP@GO₁₅), providing 74.1% decreased corrosion current and 34.2% increased corrosion potential compared to pure thermosetting powder coating. After 48 days of immersion, the electrochemical impedance spectroscopy analysis of the prepared materials revealed that the anticorrosion properties were in the sequence TP < TP@GO₁₀ < TP@GO₂₀ < TP@GO₁₅. The results indicated that addition of moderate amount of graphene oxide to prepare TP@GO coatings can significantly promote the anticorrosion performance of metals. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48264.     

Deposition and characterization of diamond coatings on WC-Co cutting tools with W/Al interlayer

A new double interlayer W/Al was developed for chemical vapor deposition (CVD) of diamond coatings on cemented WC-Co cutting tools to enhance diamond nucleation and adhesion. A thin layer of Al directly deposited on WC-Co is used to suppress the interfacial graphitization induced by Co and an additional thin layer of W is used to enhance diamond nucleation. The microstructure and adhesion of diamond coatings grown on the W/Al/WC-Co and, for comparison, on W/WC-Co as well as bare WC-Co were investigated. The results demonstrate that diamond coatings grown on W/Al are continuous and well adhesive. The advantage of the interlayer includes that nano-crystalline diamond can be achieved even under typical microcrystalline diamond growth conditions. In addition, the W/Al interlayer of overall 50–65 nm thickness would cause marginal lost of cutting edge sharpness and mechanical integrity of coated cutting tools.     

Multicomponent binders for PcBN performance enhancement in cutting tool applications

This study proposes a novel design of binders for polycrystalline cubic boron nitride (PcBN) cutting tool materials. Well-known binder phases TiC and TiN were combined with transitional metal nitrides ZrN, VN, and HfN. Performance screenings of longitudinal turning Inconel 718 and AISI 316 L highlighted the superior performance of PcBN materials with mixed TiC-ZrN and TiC-VN binders. These two systems were further sintered in a wider range of temperatures. XRD and STEM-XEDS analysis confirmed mutual dissolution of both TiC and ZrN, and TiC and VN, thus forming two types of solid solutions (Ti,Zr)(C,N) and (Ti,V)(C,N). Extended performance tests showed that tools with TiC-ZrN binder outperform reference PcBN with TiC binder by up to 20% when machining Inconel 718. When machining hardened Caldie tool steel, the performance of tools with TiC-ZrN and TiC-VN binders were 80–90% higher than the reference tools.     

PCD刀具的刃口加工方法及技术

PCD刀具是20世纪70年代以后发展起来的一种新型刀具,其优良的使用性能在现代加工工业中发挥着重要的作用,文章阐述了PCD刀具常用的刃口加工方法,即电火花加工、金刚石砂轮加工和金刚石研磨加工,具体分析了其加工方法的加工原理、影响因素、加工的状况及应用情况,说明通过合理选择PCD刀具刃口加工方法来获得良好的刃口质量,可以提高被加工工件的加工质量,延长刀具使用寿命.     

水性聚氨酯/硅溶胶复合涂层的制备与性能

将水性聚氨酯乳液与硅溶胶共混,制备了水性聚氨酯/硅溶胶复合乳液。采用TEM、激光粒度分析仪、流变仪、ATR-FTIR、TG对复合乳液及其涂膜进行表征,探讨了硅溶胶用量对复合涂膜性能的影响。ATR-FTIR分析表明,聚氨酯分子和硅溶胶之间可以形成氢键,但不存在化学键结合;TEM、激光粒度分析测试表明,硅溶胶质量分数的增加,使复合乳液粒子粒径增大,粒度分布变宽,当硅溶胶质量分数20%后,乳胶粒子间易发生团聚;流变分析发现,加入硅溶胶后,乳液的表观黏度(ηa)增大,假塑性增强。性能测试结果表明,硅溶胶质量分数20%时,复合乳液具有好的储存稳定性,复合涂膜表现出很好的热稳定性,48 h吸水率仅为18.94%,同时表现出很好的耐溶剂性能,拉伸强度达到28.98 MPa,铅笔硬度达2H,附着力0级。