常用涂层材料进展及超硬涂层技术

硬质涂层材料中,工艺最成熟、应用最广泛的是TiN。目前,工业发达国家TiN涂层高速钢刀具的使用率已占高速钢刀具的50%~70%,有的不可重磨的复杂刀具的使用率已超过90%。由于现代金属切削对刀具有很高的技术要求,TiN涂层日益不能适应。TiN涂层的耐氧化性较差,使用温度达500℃时,膜层明显氧化而被烧蚀,而且它的硬度也满足不了需要。TiC有较高的显微硬度,因而该材料的耐磨性能较好。同时它与基体的附着牢固,在制备多层耐磨涂层时,常将TiC作为与基体接触的底层膜,在涂层刀具中它是十分常用的涂层材料。TiCN和TiAlN的开发,又使涂层刀具的性能上了一个台阶。TiCN可降低涂层的内应力,     

金刚石刀具化学磨损的预防

单晶金刚石刀具因其化学磨损严重,不适用于微切削加工铁基材料.为了保护金刚石刀具免受化学磨损,可将切削刀具沉积硬质涂层,以防止金刚石与工件材料直接接触.本研究则利用磁控溅射工艺在金刚石刀具上沉积TiN、TiAlN和AlN涂层.经过优化工艺参数,所沉积涂层的化学成分接近化学计量,表面非常光滑,晶粒很细,硬度高且附着强度大.虽然刃口半径因涂层略有增加,但对微切削加工来说仍可容忍.在试验切削条件下,与参比未涂层金刚石刀具相比,TiAlN涂层金刚石刀具磨损的减少高达50%.     

镀膜时间对TiAlN薄膜的微观组织和性能的影响

本文研究了镀膜时间对TiAlN涂层的微观组织和性能的影响。研究结果表明:随着镀膜时间的延长,薄膜表面晶粒尺寸越来越细小,表面更致密度均匀;涂层硬度、膜基结合力、抗氧化性是呈先上升后下降的趋势。镀膜时间为40min时,涂层硬度达到最大值,膜基结合力、抗氧化性最好。     

涂层技术及刀具涂层知识

1,氮碳化钛（TiCN）涂层比氮化钛（TiN）涂层具有更高的硬度。由于增加了含碳量,使TiCN涂层的硬度提高了33%,其硬度变化范围约为Hv3000~4000（取决于制造商）。2,CVD金刚石涂层：表面硬度高达Hv9000的CVD金刚石涂层在刀具上的应用已较为成熟,与PVD涂层刀具相比,CVD金刚石涂层刀具的寿命提高了10~20倍。金刚石涂层刀具的高硬度,使得切削速度可比未涂层的刀具提高2~3倍,使CVD金刚石涂层刀具成为有色金属和非金属材料切削加工的不错选择。3,刀具表面的硬质薄膜对材料有如下要求：1硬度高、耐磨性能好;2化学性能稳定,不与工件材料发生化学反应;3耐热耐氧化,摩擦系数低,与基体附着牢固等。单一涂层材料很难全部达到上述技术要求。     

40CrNi2MoA合金钢阴极电弧等离子沉积TiN/TiAlN薄膜及其性能

以40CrNi2MoA钢作为基体,通过阴极电弧等离子体沉积(CPAD)技术制备了TiN、TiAlN和TiN/TiAlN薄膜。通过扫描电镜、X射线衍射仪、纳米压痕仪、原子力显微镜、摩擦磨损试验、洛氏硬度计和电化学分析,对比了3种薄膜的组织结构、纳米硬度、表面粗糙度、耐磨性、附着力和耐蚀性。结果表明,TiN/TiAlN双层膜的综合性能最佳,其附着力为HF1级,摩擦因数为0.455,纳米硬度为36.59GPa,表面粗糙度(Ra)为0.09μm。     

氮氩流量比与基底温度对射频溅射TiN薄膜性能的影响

采用射频磁控溅射技术,以纯钛为靶材,氮气为反应气体,通过改变氮氩流量比与基底温度在304不锈钢及玻璃表面制备了不同的TiN薄膜.利用能谱仪、扫描电镜、台阶仪、四探针仪、划痕仪和纳米压痕仪对制备的所制薄膜的氮钛原子比、表面形貌、沉积速率、方块电阻、膜基结合力和纳米硬度进行表征.结果表明:随着氮氩流量比的增大,TiN的形貌先由四面锥体凸起结构逐渐过渡至柱状晶体堆积结构,然后转变为稀疏的液滴状颗粒结构,直至平整光滑,致密均匀.在氮气和氩气的流量分别为5.0 mL/min和50.0 mL/min的条件下,基底温度25～400°C范围内制备的TiN薄膜的结合力介于135.4 mN与210.2 mN之间.当基底温度为300℃时,薄膜的沉积速率最大,颜色最接近金黄色,氮钛原子比最接近1,结合力和纳米硬度也都最大.     

膜厚对(Ti,Al)N涂层微结构、机械性能及切削特性的影响

利用蒸发与磁控溅射二元组合源设备,通过控制沉积时间在钨钴类硬质合金螺纹刀表面制备了不同膜厚的(Ti,Al)N涂层。采用X射线衍射仪、扫描电镜、能谱仪、维氏显微硬度计、洛氏硬度计和摩擦试验机考察了涂层厚度对涂层微观结构、表面形貌、元素组成、显微硬度、膜-基结合力及摩擦磨损性能的影响,并通过切削40Cr钢材研究了涂层刀具的切削特性。结果表明,沉积6 h所得涂层(膜厚约5.0μm)的复合硬度(涂层+基材的显微硬度)显著高于沉积2 h(膜厚约1.8μm)所得涂层,但膜-基结合力更弱,磨耗速率更快。     

超硬薄膜涂层材料研究进展及应用

采用CVD和PVD法制备TiN．TiC．TiCN．TiAlN等硬质薄膜涂层材料已经在工具、模具、装饰等行业得到日益广泛的应用．但仍然不能满足许多难加工材料．如高硅铝合金，各种有色金属及其合金，工程塑料，非金属材料．陶瓷，复合材料（特别是金属基和陶瓷基复合材料）等加工的要求。正是这种客观需求导致了诸如金刚石膜、立方氮化硼（C-BN）和碳氮膜（CNx）以及纳米复合膜等新型超硬薄膜材料的研究进展。笔者对这些超硬材料薄膜的研究现状及工业化应用前景进行了简要的介绍和评述。     

合肥工大纳米氮化钛陶瓷刀具通过技术鉴定

合肥工业大学材料学院主持的国家科技攻关重大项目“纳米TiN、AIN改性的TiC基金属陶瓷刀具制造技术”近日通过国家有关部门鉴定。这标志着我国利用纳米材料研制的新型陶瓷刀具开发成功。据悉，该项目研究的纳米TiN（氮化钛）改性TiC基金属陶瓷材料，采用在金属陶瓷TiC中引入纳米TiN细化颗粒的方法。晶粒的微细化有利于提高材料的强度、硬度与断裂韧性，对于开发研制新型刀具具有重要意义。纳米TiN改性TiC基金属陶瓷刀具有着优良的力学性能，具备高技术含量与高附加值产品的特点。经过实际使用证明，它在切削加工领域可取代YC8、YT15等硬质合金刀具。刀具使用寿命可提高两倍以上。     

阴极电弧制备AlTiN和TiAlSiN涂层的性能及铣削性能

采用阴极电弧离子镀技术在YG10硬质合金试片及铣刀上分别制备了厚度为为2.604μm和2.798μm的纳微米AlTiN和TiAlSiN涂层,采用实验方法研究涂层的微观结构、力学性能,以及涂层刀具铣削HT200时的铣削性能。实验研究结果表明:制备的AlTiN及TiAlSiN涂层的硬度分别为29.14 GPa及38.94 GPa,Si元素的添加细化涂层组织结构,TiAlSiN涂层的断面结构更为致密,涂层的硬度及耐磨性显著增加。AlTiN及TiAlSiN涂层与基体的结合强度等级分别满足工业等级的HF3、HF1要求,TiAlSiN涂层表现出较好的膜基结合性能。相较于AlTiN涂层,TiAlSiN涂层刀具表现出较小的切削力。此外,TiAlSiN涂层比AlTiN涂层拥有较好的抵抗磨损的能力。     

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.     

Characterization of TiCN and TiCN/ZrN coatings for cutting tool application

Coating a cutting tool improves wear resistance and prolongs tool life. Coating performance strongly depends on the mechanical and chemical properties of the coating material. In a machining process, the type of selected coating depends on the cutting condition because of the properties of the applied coating material. In addition, many factors, such as coating thickness, composition ratio, sequences of layers in multilayer coatings, and the deposition method influence the performance of a coating. In this study, the mechanical properties of TiCN and TiCN/ZrN were investigated using a ball on disk test. The substrate material made from a carbide-based cutting tool was also developed in-house. The analysis performed shows that the performances of TiCN and TiCN/ZrN coatings were found to be comparable to that of the commercial TiN-coated carbide-based cutting tool. Both the in-house and commercial coated inserts had significantly lower coefficient of friction than uncoated inserts, and the friction coefficient of TiCN coatings was constantly slightly lower than that of TiN coatings. Moreover, the coefficient of friction of the in-house developed TiCN was slightly lower than that of commercial TiN coating. However, the coefficient of friction of the in-house developed uncoated carbide inserts was slightly higher than that of commercial uncoated carbide inserts.     

Wear-Resistant Titanium Carbonitride Coatings onto WC–Co Cutting Tools by Pulsed High-Energy Density Plasma

Nanometer grain superhard ternary Ti(C,N) coatings with Vicker's nanohardness more than 50 GPa were deposited onto WC–Co cutting tools at ambient temperature using pulsed high-energy density plasma coaxial gun. Young's modulus of the coated tools was about 550 GPa. Because of the continuously graded interfaces between the coatings and substrates, the coatings are well adherent to the tool substrates with very high critical load up to more than 100 mN measured by nanoscratch tester. The coefficients of friction were lower than 0.1. In contrast with the uncoated tools, the coated tools could be applied in turning hardened CrWMn steel at high speed under industrial conditions without lubricants, and the cutting performances were greatly improved with rather low flank wear and long tool life.     

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.     

Properties of TiN–Al2O3–TiCN–TiN,TiAlN, and DLC-coated Ti(C,N)-based cermets and their wear behaviors during dry cutting of 7075 aluminum alloys

In the work, TiAlN for physical vapor deposition (PVD), multilayer TiN-Al₂O₃-TiCN-TiN for chemical vapor deposition (CVD), and diamond-like carbon (DLC) for plasma-enhanced chemical vapor deposition (PECVD) were deposited on the cermet inserts. Characteristics and wear behaviors of the three coated cermets during dry cutting of 7075 aluminum alloys were observed. The results show that TiN-Al₂O₃-TiCN-TiN coatings have highest adhesion strength and hardness. At the cutting speed of 1100 r/min, the depth of 0.2 mm, and the feed rate of 0.1 mm/r, the three coated inserts show the best wear-resistant properties. In this case, TiN/Al₂O₃/TiCN/TiN shows the worst wear-resistant properties (value of the flank wear [VBB] = 0.062 mm), while DLC coatings show the most excellent wear-resistant properties (VBB = 0.046 mm). During the cutting of aluminum alloys, which have high plasticity and low melting point, adhesive wear dominate on the flank of the inserts. The thickest coating of TiN/Al₂O₃/TiCN/TiN results in the bluntest cutting edge, which form the most serious adhesive worn zone. For the TiAlN and DLC coatings, due to a smaller cutting force, the two coatings have much better wear resistance. Further, the self-lubricating properties of DLC show excellent effect on protecting the inserts. Thus, the DLC-coated cermets have the best wear-resistant properties. Further, the TiAlN-coated cermets have the widest wear-affected zone while the DLC coating has the narrowest.     

Correlation of the fatigue impact resistance of bilayer and nanolayered PVD coatings with their cutting performance in machining Ti6Al4V

Titanium alloys are widely employed in aerospace and biomedical applications. During the cutting process of Ti6Al4V alloy, the material characteristics of high specific strength and poor thermal conductivity lead to a stress concentration occurred at the tool/chip interface, which may cause severe failure of the coated tools. Besides, the titanium alloy gives rise to serrated chips, whose thickness varies regularly in the cycle mode, which lead to the variation of cutting force and tool stress. So a cyclic impact with high frequency is applied on the coated tool surface, and this induces the fatigue fracture of coating. In this study, repetitive contact between the coating and Vickers diamond indenter through the high frequency cyclic impact tester was developed by employing the ultrasonic actuator device. High frequency cyclic impact testing has been used to study the impact resistance of the TiSiN/TiAlN bilayer coating and TiSiN/TiAlN nanolayered coating. Besides, stress concentration resulting in the failure of coatings can be generated by using the sharp Vickers indenter. The crack propagation in coatings was investigated by the scanning electron microscope (SEM), and the fracture processes of coatings were studied from the force measurement data acquisition system. In addition, the cutting performance of cemented carbide tools coated with these two coatings was evaluated in turning Ti6Al4V titanium alloy. The correlation between the fatigue impact resistance of coatings at high frequency and the wear behavior of coated tools under different cutting conditions was studied. It can be concluded that the TiSiN/TiAlN nanolayered coating showed better properties to resist fatigue impact at the lower impact load, but worse properties to resist fatigue impact at the higher impact load.     

Effects of tool coating materials and coating thickness on cutting temperature distribution with coated tools

Coated tools are currently widely used tool technology in machining. The influence of tool coating on heat transfer has become an active field of research enjoying constantly increasing attention in the field of machining. This paper is devoted to the cutting temperature in machining H13 hardened steel with monolayer coated tools (TiN, TiAlN, and Al₂O₃) and multilayer coated tools (TiN/TiC/TiN and TiAlN/TiN). Equivalent composite thermal conductivity and thermal diffusivity of multilayer coated tools were calculated using the equivalent approach. The established heat transfer analytical models estimated coating temperature in turning. The effect of tool coating in steady and transient heat transfer was studied, as well as the cutting temperature distribution. It reveals that the tool coating material and coating thickness can influence the cutting temperature distribution of coated tool. Thermal conductivity of coating material affects the steady cutting temperature distribution, and thermal diffusivity of coating material affects the transient cutting temperature distribution of coating tools.     

Improvement of structural/tribological properties and milling performances of tungsten carbide cutting tools by bilayer TiAlN/TiSiN and monolayer AlCrSiN ceramic films

In this study, bilayer TiAlN/TiSiN and monolayer AlCrSiN ceramic films were grown on carbide cutting tool material by cathodic arc physical vapor coating (CAPVD) method to improve the structural/tribological properties and milling performances. The ceramic films were applied on cylindrical test samples and carbide end mills. The coated materials' structural, mechanical, and tribological properties were determined via scanning electron microscope (SEM), X-ray diffraction meter (XRD), tribometer, microhardness tester, and optical profilometer. DIN 40CrMnNiMo8-6-4 steel workpieces were machined by using a CNC vertical machining center to determine the actual working performance of the coated and uncoated cutting tools. The wear performance of the cutting tools after machining was determined by measuring the flank wear widths and mass losses. The hardness and adhesion results of the coated sample with bilayer TiAlN/TiSiN were higher than the coated sample with monolayer AlCrSiN. According to the scratch test results, the best adhesion results were obtained for TiAlN/TiSiN coating. The critical load value was determined as about 105 N. As a result, the wear rate value of the TiAlN/TiSiN thin film coated sample was lower. After machining, the mass loss of TiAlN/TiSiN coated tools was lower than AlCrSiN coated tools. In addition, the surface roughness value of the workpiece machined by the cutting tool coated with AlCrSiN was higher than the cutting tool coated with TiAlN/TiSiN.     

Performance and wear mechanism of spark plasma sintered WC-Based ultrafine cemented carbides tools in dry turning of Ti–6Al–4V

Cutting performance and failure mechanisms of spark plasma sintered (SPS) ultrafine cemented carbides in dry turning Ti–6Al–4V were studied. The tools of UYG8 (WC-8wt%Co) and UYG8V2B10 (WC-8wt%Co-0.2 wt%VC-1.0 wt%cBN) exhibited higher lifetime and better processing quality than the commercial YG8 cemented carbide tool. The cutting distance of UYG-8 and UYG8V2B10 tools are 1.8 and 1.6 times longer than that of YG8, respectively. Cutting-edge breakage was found as the main failure forms of the SPS cemented carbide tools containing low Co content (≤6 wt%), whereas the SPS cemented carbide tools containing high Co content (≥8 wt%) exhibited flank and rake wear as main failure forms caused by abrasion, adhesion, diffusion, and oxidation. UYG8V2B10 tool wear mechanism was affected by cutting speed and depth. Wear mechanisms of UYG8V2B10 tool are mainly adhesive wear and oxidative wear at low cutting speed, but follow adhesive wear and diffusive wear at higher cutting speed. Moreover, with increasing cutting depth, tool failure forms are mainly breakage and chipping, largely induced by high cutting temperature and severe cutting vibration.     

A study of CVD diamond deposition on cemented carbide ball-end milling tools with high cobalt content using amorphous ceramic interlayers

In this paper, CVD diamond coatings are deposited on cemented carbides with 10 wt.% Co using amorphous SiO₂ and amorphous SiC interlayers. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Raman spectrum and X-ray diffraction (XRD) are carried out to characterize the microstructure and composition of as-deposited films. Moreover, the adhesion and cutting performance of as-fabricated diamond coatings are studied. Indentation tests show that the amorphous ceramic interlayers can enhance the adhesion between diamond films and WC–Co substrates. The cutting tests against zirconia indicate that the tools with amorphous ceramic interlayered diamond coatings exhibit improved cutting performance. The amorphous ceramic interlayers can improve the adhesive strength and wear endurance of diamond coatings on WC–10 wt.% Co substrates, which provide a viable way for adherent diamond coatings on cemented carbide tools with high cobalt content.