Tribological property and drilling application of Ti-C:H and Cr-C:H coatings on high-speed steel substrates

This study investigates the tribological properties and cutting performance of Ti-DLC and Cr-DLC doped metal coatings. The tribological properties of the coatings are evaluated by testing coated disks against an AISI 1045 steel counterbody under dry conditions using an oscillating friction wear tester, and then measuring the subsequent wear depth on the coated disk, the wear width on the steel counterbody, and the friction coefficient. The cutting performance of the coatings is evaluated by using coated high-speed drills to machine stainless steel workpieces, and then measuring the resulting flank wear and hole surface roughness. The results of the wear tests show that the Ti-C:H and Ti-C:H/TiC/TiCN/TiN coatings possess excellent tribological properties, including low coefficients of friction, low wear depths, and low wear widths. Regarding the machining tests, the Ti-C:H/TiC/TiCN/TiN coating has the lowest flank wear and yields the highest hole surface quality under both dry and cutting fluid drilling conditions. The single Ti-C:H coating has excellent tribological properties, but demonstrates a relatively poorer performance in the drilling of stainless steel. Finally, the Cr-DLC coatings all exhibit a poor cutting performance under dry cutting conditions.     

An experimental investigation into the influence of ZrN and TiN coatings on drills in drilling Hasteloy

This paper presents a comparison of the performance characteristics of titanium nitride (TiN) and zirconium nitride (ZrN) coatings on drills. The objective of this work was two-fold: to choose the best coating for machining tough materials tike Hasteloy; and to determine a method of predicting the wear of drills. A longer life of drills leads to increased productivity of drilling holes in certain components of environmental-control systems and fuel-control assemblies (in the aerospace industry) made of tough materials like Hasteloy. The comparison of the two coatings and tool wear was based on the measurement of static and dynamic forces and torques, power spectral density and acoustic-emission plots. The measurements were carried out using piezoelectric dynamometers and an acoustic-emission device. Upon analysis of the data, it was found that drills coated with TiN performed better than those coated with ZrN. It was also observed that the root-mean-square value of the acoustic-emission density and power spectral plots are good indicators for the prediction of tool wear.     

Corrosion behaviour of decorative and wear resistant coatings on steel deposited by reactive magnetron sputtering - Tests and improvements

Depositions of decorative and wear resistant single layer coatings like TiN, Ti(B,N), CrN, NbN, NbON, (Ti,Mg)N and multilayer coatings like Cr/CrN, Nb/NbN, CrN/NbN and NbN/Nb-C:H were performed using reactive magnetron sputtering. The corrosion behaviour of the coated high speed steel substrates was studied in sodium chloride containing media by open-circuit-potential measurements, potentiodynamic corrosion tests and salt spray tests. Up to now, the best improvements with respect to the corrosion resistance in salt spray tests could be obtained for the system (Ti,Mg)N/high speed steel.     

基于TiC_(0.5)N_(0.5)/Si_3N_4复相陶瓷基体的PVD及CVD涂层刀具性能

首先,以15vol%或25vol%的TiC0.5N0.5粉体为导电第二相,利用热压烧结法制备了TiC0.5N0.5/Si3N4复相陶瓷;然后,分别通过物理气相沉积(PVD)和化学气相沉积(CVD)技术在TiC0.5N0.5/Si3N4陶瓷刀具表面沉积了CrAlN和TiN/Al2O3/TiN涂层;最后,通过对TiC0.5N0.5/Si3N4刀具进行连续切削灰铸铁实验,研究了TiC0.5N0.5含量和涂层类型对刀具磨损特征的影响,并探讨了刀具的磨损机制。结果表明:TiC0.5N0.5含量的增加有利于提高TiC0.5N0.5/Si3N4复相陶瓷刀具基体的硬度和电导率,但对耐磨性和切削寿命的影响较小;采用PVD技术沉积CrAlN涂层时,随着TiC0.5N0.5含量的增加,涂层的厚度、结合强度和硬度都得到提高,涂层刀具的磨损性能显著提高,切削寿命也明显延长;而采用CVD技术沉积TiN/Al2O3/TiN涂层时,TiC0.5N0.5含量的变化对涂层的厚度、结合强度和硬度基本没有影响,TiN/Al2O3/TiN涂层刀具整体切削性能变化不大。CrAlN涂层和TiN/Al2O3/TiN涂层都可明显改善TiC0.5N0.5/Si3N4复相陶瓷刀具的耐磨性和切削寿命;相对于TiN/Al2O3/TiN涂层,CrAlN涂层具有更高的涂层硬度和粘着强度,但TiN/Al2O3/TiN涂层具有较大的涂层厚度,TiN/Al2O3/TiN涂层刀具表现出更加优异的耐磨性和切削寿命。TiC0.5N0.5/Si3N4复相陶瓷刀具的磨损机制以机械摩擦导致的磨粒磨损为主,伴随有少量的粘结磨损。     

Effect of Heat Treatment on the Drilling Performance of Aluminium/SiC MMC

The extremely abrasive reinforcing phases present in metal matrix composites (MMCs) are known to dominate their machining behaviour. Consequently, the properties of the matrix material are often ignored. The work reported here investigated the influence of matrix microstructure on the drilling performance of a 2618 aluminium alloy reinforced with 18% silicon carbide particles. The drills used were 8 mm diameter, titanium nitride coated K10 carbide with through-tool cooling. The workpiece material was drilled in four heat treatment conditions: as-extruded, solution treated and solution treated and aged for 12 and 20 hours. Drilling performance was assessed by measuring the wear on the drills, cutting forces, surface finish and the condition of the worn cutting edges. The results indicated that softer as-extruded and solution treated materials produced less wear and lower cutting forces than the harder aged materials. However, the height of the burrs produced during drilling were found to be greater with the softer materials and the quality of the drilled surface was also inferior. Examination of the worn cutting edges indicated that the wear mechanism was primarily one of abrasion although some attrition and edge chipping was also observed. It was concluded that when drilling these materials, the heat treatment condition of the matrix exerts a significant influence on machinability.     

添加元素对TiN涂层磨损机理的影响

利用ＡＥＳ，ＸＲＤ和ＷＤＳ等手段研究了Ｗ１８Ｃｒ４Ｖ钢表面用多弧离子镀技术沉积ＴｉＮ涂层中添加Ａｌ，Ｃ等元素对涂层磨损机理的影响，试验结果表明，ＴｉＡｌＮ涂层限ＴｉＮ的相同，仍以微剥落为主要失效形式，而ＴｉＣＮ则在磨损接触面上形成了界面层，磨损过程就是界面层向涂层内部的迁移过程。     

离子镀硬质膜技术的最新进展和展望

电弧离子镀至今仍是硬质膜的主流技术,但是,其内容与８０年代比已大为丰富。首先,镀层材料由单一氮化钛,发展到氮化钛与碳氮化钛,氮化钛铝,氮化铬等多种材料并用。然后,又进一步发展为多层复合镀层。远离平衡态过程听低温沉积技术日趋成熟。使各种机械零件的需磨损磨腐蚀底层逐步走向实用化,促进了机械戒严水平全面提高。低温沉积技术大幅度降低镀层内应力,使镀层的厚度能够达到数十,甚至上百微米,满足了发展高性能特性镀     

氮化物硬质涂层中Cr、Ti和Al元素对摩擦磨损特性的影响

利用四靶闭合场非平衡磁控溅射(CFUBMS)技术在石英玻璃和抛光不锈钢片两种基底上制备含有Cr、Ti和Al元素组合的各种氮化物涂层.采用摩擦磨损仪测试涂层摩擦系数,应用金相显微镜对各个涂层磨痕形态进行分析,结果表明TiN、CrN、TiAlN、CrAlN以及CrTiAlN涂层的摩擦系数依次减小,耐磨特性依次提高;结合涂层的X射线光电子能谱分析,可以得到含有Al元素涂层中形成了AlN的结构,提高涂层的硬度,增加耐磨特性;在涂层中含有Cr元素形成了氧化物Cr2O3可以提高涂层自排屑能力,减小摩擦系数,增加耐磨特性,含Ti元素形成的氧化物TiO2则不利于涂层的摩擦磨损特性;由于CrTiAlN本身具有比三元氮化物更高的涂层硬度,且含有Al和Cr元素,因此该涂层具有最好的摩擦磨损性能.     

On Applicability of Multilayer Coated Tool in Dry Machining of Aerospace Grade Stainless Steel

The present research work has been undertaken with a view to investigate the influence of CVD multilayer coated (TiN/TiCN/Al₂O₃/ZrCN) and cutting speed on various machining characteristics such as chip morphology, tool wear, cutting temperature, and machined surface roughness during dry turning of 17-4 PH stainless steel. In order to understand the effectiveness of CVD multilayer coated tool a comparison has been carried out with that of uncoated carbide insert. The surface roughness and cutting temperature obtained during machining with chemical vapor deposition (CVD) multilayer coated tool was higher than that of uncoated carbide insert at all cutting velocity. However, the results clearly indicated that CVD multilayer coated tool played a significant role in restricting various modes of tool failure and reducing chip deformation compared to its uncoated counterpart. Adhesion and abrasion were found to be dominating wear mechanism with flank wear, plastic deformation, and catastrophic failure being major tool wear modes.     

基于PVD-TiN和TiSiN涂层的Al2O3/TiCN陶瓷刀具及其切削性能研究

采用物理气相沉积(Physical vapor deposition, PVD)工艺在Al₂O₃/TiCN陶瓷刀具表面分别沉积了TiN和TiSiN涂层。通过扫描电子显微镜(SEM)观察涂层微观结构, 采用显微硬度计和划痕仪分别表征涂层硬度和测量涂层与基体的结合强度。通过对涂层刀具进行连续干切削灰铸铁实验, 研究TiN和TiSiN涂层对刀具磨损特征的影响并探讨其磨损机理, 同时研究了涂层对工件加工表面质量的影响。结果表明: PVD涂层可显著提高Al₂O₃/TiCN陶瓷的刀具硬度。TiN涂层和TiSiN涂层可分别提高刀具表面硬度25%和65%, 从而增加刀具耐磨性。两种涂层刀具在连续切削灰铸铁实验中主要的失效机理均是挤压变形下的磨粒磨损, 其中TiN涂层刀具还伴随有粘结磨损; 刀具上的PVD-TiN和TiSiN涂层可以有效保护Al₂O₃/TiCN陶瓷刀具基体, 防止崩刃, 进而改善工件表面加工质量。     

Characterization and Performance of AlTiN,AlTiCrN, TiN/TiAlN PVD Coated Carbide Tools While Turning SS 304

This study presents the physical, mechanical properties and dry turning performance of AlTiN, AlTiCrN, and TiN/TiAlN coatings produced on K-grade tungsten carbide insert by advanced physical vapor deposition technique. Scanning electron microscopy, microhardness tester, and scratch tester were used to examine surface morphology, coating thickness, microstructure, microhardness, and adhesion of coating. The performance in terms of cutting force and temperature of AlTiN, AlTiCrN, and TiN/TiAlN coated inserts was evaluated while dry turning of SS 304 steel. SS 304 is considered as “difficult-to-cut” material due to its exotic properties. The experiments were conducted at cutting speed of 140, 200, 260, and 320 m/min. Feed and depth of cut were kept constant and their values were 0.20 mm/rev and 1 mm, respectively. Experimental observations depicts that AlTiCrN coated insert demonstrated better performance because of its good adhesion and high oxidation resistance followed by TiN/TiAlN coated insert. TiN/TiAlN coated insert exhibited higher cutting temperature than AlTiCrN and AlTiN coated inserts. The findings of the study should also provide economic machining solution in case of dry turning of SS 304 stainless steel.     

Comparing the Effectiveness of Coatings on Carbide andCermet Cutting Tool Inserts

A series of metal cutting experiments was performed on a CNC lathe to evaluate the performance of various coatings on different tool substrates. The workpiece material was plain medium carbon steel and the cutting tool materials were carbide and cermet inserts coated with various single as well as multilayer coatings. Machining was done under various cutting conditions of speed and feed-rate, and for various durations of Cutting. The output parameters studied were the cutting forces (axial, radial and tangential), the surface roughness of the workpiece, as well as the tool wear (crater and flank wear). From these results, the performances of the various cutting inserts are evaluated and compared. Results show that cutting forces are significantly lower when using coated cermets than when using coated carbides although different coatings on the same substrate also result in different cutting forces. However, there is less difference in the surface roughness of the finished workpiece for the various coatings and substrates.     

CrAlTiN镀层在精密铣刀上的应用研究

介绍了通过闭合场非平衡磁控溅射离子镀技术制备出的CrAlTiN超硬纳米梯度复合镀层在铣刀上的应用,试验结果表明,铣刀在离子镀处理之后寿命提高为原来的3倍.采用SEM和TEM分析了镀层铣刀磨损后的表面形貌及无镀层铣刀的失效方式,揭示了镀层提高铣刀寿命的原因.     

A study on the abrasive and erosive wear behavior of arc-deposited Cr-N-O coatings on tool steel

In this study, the cathodic arc evaporation technique, by using the chromium target and controlling the flow rate of nitrogen/oxygen reactive gases, was utilized to deposit three different Cr-N-O coatings (CrN, CrN/Cr(N,O), CrN/Cr₂O₃) on AISI M2 tool steel. Two types of wear tests were applied to evaluate the abrasive and erosive wear behavior of the coated and uncoated specimens. One was the ball-on-disk abrasion test to measure the friction coefficient of these specimens. The other was the erosion test using Al₂O₃ particles (~ 177 µm in size and Mohr 7 scale) of about 5 g, and then the surface morphologies of the eroded specimens were observed. To further understand the coating effects on the two wear behaviors of M2 steel, coating structure, morphology, and adhesion were analyzed using XRD, SEM, and TEM, respectively. The results showed that surface roughness and adhesion of the double-layered coatings (CrN/Cr(N,O) and CrN/Cr₂O₃) were inferior to those of monolithic CrN, but their hardness and elastic modulus were superior to those of CrN. In the abrasive behavior, Cr-N-O coatings reduced the friction coefficient of M2 substrate. In particular, the CrN/Cr₂O₃ has the highest hardness/elastic (H/E) modulus ration, therefore the lowest friction coefficient, among all the coated-specimens tested. In the erosive behavior, the coated specimens exhibited better erosion resistance as compared to the uncoated ones, at the impingement angles of either 30^o or 90^o. Moreover, the erosion resistance of CrN/Cr(N,O) coatings was superior to that of CrN/Cr₂O₃ coatings due to its better adhesion.     

激光熔覆原位自生TiC颗粒增强镍基复合涂层的组织与耐磨性

采用预置粉末法在45钢表面进行激光熔覆镍基Ni60A+x%(SiC+Ti)(质量分数,下同)复合粉末涂层的实验研究。使用往复式磨损试验机对不同涂层材料的熔覆层进行干摩擦磨损实验,利用金相显微镜、扫描电镜(SEM)观察和分析熔覆层的显微组织与磨损形貌。结果表明:复合粉末通过原位反应生成弥散分布的TiC颗粒增强复合涂层,随着(SiC+Ti)含量的增加,颗粒状TiC的尺寸和数目逐渐增加;复合粉(SiC+Ti)含量达到60%时,微观组织有气孔和夹杂缺陷;复合粉(SiC+Ti)含量为48%时,熔覆层耐磨性最佳;复合涂层的磨损主要为磨粒磨损,机理为微观切削和挤压剥落。     

Performance evaluation of reactive direct current unbalanced magnetron sputter deposited nanostructured TiN coated high-speed steel drill bits

The stainless steels, in general, are considered to be difficult-to-machine materials. In order to machine these materials the surface of the tool is generally coated with physical vapour deposition (PVD) hard coatings such as titanium nitride (TiN), titanium aluminum nitride (TiAlN), etc. The adhesion is of vital importance for the performance of tools coated with PVD coatings. Proper surface treatments (in situ and ex situ) are required to achieve highly adherent PVD coatings on tools. We have deposited nanostructured TiN coatings on high-speed steel (HSS) drill bits and mild steel substrates using an indigenously built semi-industrial four-cathode reactive direct current (d.c.) unbalanced magnetron sputtering system. Various treatments have been given to the substrates for improved adhesion of the TiN coatings. The process parameters have been optimized to achieve highly adherent thick good quality TiN coatings. These coatings have been characterized using X-ray diffraction, nanoindentation and atomic force microscopy techniques. The performance of the coated HSS drill bits is evaluated by drilling a 13 mm thick 304 stainless steel plate under wet conditions. The results show significant improvement in the performance of the TiN coated HSS drill bits.     

Investigation on Some Machinability Aspects of Inconel 825 During Dry Turning

In the current study, attempt has been made to investigate the influence of cutting speed (Vc) (51, 84, and 124 m/min) on various machining characteristics like chip morphology, chip thickness ratio, tool wear, surface, and sub-surface integrity during dry turning of Inconel 825. Comparable study was carried out using uncoated and commercially available chemical vapor deposition multilayer coated (TiN/TiCN/Al₂O₃/ZrCN) cemented carbide (ISO P30 grade) insert. Chip morphology consists of chip forms obtained at different cutting conditions. Serrated chips were observed when machining Inconel 825 with both types of tool with more serration in case of uncoated insert. The chip thickness ratio increased as cutting speed was increased. Use of multilayer coated tool also resulted in increase in chip thickness ratio. Rake and flank surfaces were examined with scanning electron microscope and optical microscope. Abrasion, adhesion, and diffusion wears were found to be dominating tool wear mechanism during dry machining of Inconel 825. The beneficial effect of coated tool over its uncoated counterpart was most prominent during machining at high cutting speed (Vc = 124 m/min). The surface and sub-surface integrity obtained with coated tool were superior to that while machining Inconel 825 with uncoated tool.     

HF-CVD of diamond coatings onto Fluidized Bed (FB) treated CrN interlayers

In the present investigation, Fluidized Bed (FB) treatment is applied to pre-treat CrN interlayers onto WC-Co substrates to promote the growth on them of highly adherent diamond coatings. During FB treatment, the CrN interlayers are submitted to high speed impacts of loose abrasives. The action of their cutting edges is able to deeply change the starting morphology of the as-deposited Physical Vapour Deposition (PVD) CrN interlayers, thus promoting the establishment of a highly corrugated surface on which to grow Hot Filament-Chemical Vapour Deposition (HF-CVD) diamond coatings.Growth, morphology, adhesion and wear resistance of the CVD deposited diamond coatings onto the FB treated and just seeded CrN interlayers were looked into and compared to diamond coated WC-Co substrates with the untreated CrN interlayers or pre-treated with a two-step chemical etching (Murakami's reagent and Caro's acid, MC-treatment) or with FB.FB treatment proved to be an effective technique to tailor the surface morphology and roughness of CrN films deposited by PVD-arc technique, and was found to be very useful in improving the adhesion and wear resistance of CVD diamond onto the CrN interlayers.     

Wear of surface engineered metal-on-metal hip prostheses

The wear of existing metal-on-metal (MOM) hip prostheses (1 mm3/million cycles) is much lower than the more widely used polyethylene-on-metal bearings (30-100 mm3/million cycles). However, there remain some potential concerns about the toxicity of metal wear particles and elevated metal ion levels, both locally and systemically in the human body. The aim of this study was to investigate the wear, wear debris and ion release of fully coated surface engineered MOM bearings for hip prostheses. Using a physiological anatomical hip joint simulator, five different bearing systems involving three thick (8-12 microm) coatings, TiN, CrN and CrCN, and one thin (2 microm) coating diamond like carbon (DLC) were evaluated and compared to a clinically used MOM cobalt chrome alloy bearing couple. The overall wear rates of the surface engineered prostheses were at least 18-fold lower than the traditional MOM prostheses after 2 million cycles and 36-fold lower after 5 million cycles. Consequently, the volume of wear debris and the ion levels in the lubricants were substantially lower. These parameters were also much lower than in half coated (femoral heads only) systems that have been reported previously. The extremely low volume of wear debris and concentration of metal ions released by these surface engineered systems, especially with CrN and CrCN coatings, have considerable potential for the clinical application of this technology.     

Corrosion protection of CrN/TiN multi-coating for bipolar plate of polymer electrolyte membrane fuel cell

The electrochemical corrosion cells will be generated from the possible pinholes of the promising CrN and TiN coatings in a PEMFC environment. To prevent the elution of possible pinholes, CrN/TiN multi-coatings on SS have been considered. This study examined the electrochemical behavior of three CrN/TiN coatings on 316L stainless steel deposited at different CrN/TiN thickness ratios by rf-magnetron sputtering as potential bipolar plate materials. Potentiodynamic tests of CrN/TiN-coated 316L stainless steel carried out in a 1 M H₂SO₄ + 2 ppm HF solution at 70 °C revealed a significantly lower corrosion current density than that of uncoated 316L SS, as well as a decrease in the corrosion current density with decreasing inner-layer CrN thickness. Electrochemical impedance spectroscopy also showed that the CrN/TiN-coated 316L SS sample had higher charge transfer resistance than the uncoated 316L SS sample, which increased with decreasing inner-layer CrN thickness. This was attributed to the crystalline-refined CrN/TiN(200).