Tribological Behavior of TiAlN,AlTiN, and AlCrN Coatings at Boundary Lubricating Condition

In this study, ~?3.5 µm thick multilayer titanium alumina nitride (TiAlN), alumina titanium nitride (AlTiN), and alumina chromium nitride (AlCrN) coatings were deposited on the H13 steel surface by cathodic arc physical vapor deposition (CAPVD) method. The tribological performance of the coatings was evaluated by a tribometer at boundary lubrication condition. Then, coating surfaces were observed by optical microscope, optical profilometer, and atomic force microscope to evaluate the morphological changes, wear volumes, and tribofilm thickness. Also, scanning electron microscopy (energy dispersive X-ray) and X-ray photoelectron spectrometry analyses were applied to coating surfaces for the tribochemical evolution of the tribofilm. Results showed that AlCrN coating performed the best tribological behavior at boundary lubricated condition, when compared to TiAlN and AlTiN coatings and it can be used as a wear resistant cam tappet coating in internal combustion engines.     

Abrasive Wear of DLC/PVD Multilayer Coatings: AFM Studies

The tribological behaviour of multilayered coatings deposited on plain carbon steel was investigated by microscale abrasion tests (MSATs). The multilayered coatings consisted of an outer diamond‐like carbon (DLC) layer, a physical vapour deposition (PVD) nitride‐based interlayer, and an inner electroless Ni‐P layer. PVD TiN‐ and Ti(C,N)‐coated samples with and without the DLC outer layer were studied in order to evaluate the influence of each layer on the tribological behaviour of the multilayer‐coated system. The MSATs were carried out using a device based on ball‐cratering geometry: a hard steel sphere was rotated against the coated specimen in the presence of an aqueous suspension of SiC particles. The wear coefficients of the multilayers were calculated from the diameter of the wear craters. The morphology of the wear scars produced by the MSATs was studied by atomic force microscopy (AFM). The wear damage was described by measuring the r.m.s. roughness (S_q) on the sides of the wear craters. Roughness values were related to the wear coefficients (k_c) for the different multilayers on the basis of mathematical elaboration typical of the ‘design of experiment’ (DOE) statistical technique. The presence of the DLC outer layer reduced the roughness of the crater sides and significantly increased the wear resistance of the multilayer only in the case of the PVD TiN sublayer.     

Tribological behavior of TiN films depositid by reactive magnetron sputtering under low pressure

The effect of deposition conditions on the tribological behavior of titanium nitride thin films produced by reactive magnetron sputtering has been studied. Dependences of the hardness, the width of the friction track, the friction coefficient, and the volume wear of the TiN films on the N₂ reactive gas flow rate have been obtained. Conditions of deposition under which the coatings with the best tribological characteristics are formed have been determined.     

Substrate Effects on the Micro/Nanomechanical Properties of TiN Coatings

Nanoindentation and nanoscratch tests were performed for titanium nitride (TiN) coatings on different tool steel substrates to investigate the indentation/scratch induced deformation behavior of the coatings and the adhesion of the coating–substrate interfaces and their tribological property. In this work, TiN coatings with a thickness of about 500 nm were grown on GT35, 9Cr18 and 40CrNiMo steels using vacuum magnetic-filtering arc plasma deposition. In the nanoindentation tests, the hardness and modulus curves for TiN/GT35 reduced the slowest around the film thickness 500 nm with the increase of indentation depth, followed by TiN/9Cr18 and TiN/40CrNiMo. Improving adhesion properties of coating and substrate can decrease the differences of internal stress field. The scratch tests showed that the scratch response was controlled by plastic deformation in the substrate. The substrate plays an important role in determining the mechanical properties and wear resistance of such coatings. TiN/GT35 exhibited the best load-carrying capacity and scratch/wear resistance. As a consequence, GT35 is the best substrate for TiN coatings of the substrate materials tested.     

ANN-based prediction of surface and hole quality in drilling of AISI D2 cold work tool steel

This paper focuses on artificial neural network (ANN)-based modeling of surface and hole quality in drilling of AISI D2 cold work tool steel with uncoated titanium nitride (TiN) and titanium aluminum nitride (TiAlN) monolayer- and TiAlN/TiN multilayer-coated-cemented carbide drills. A number of drilling experiments were conducted at all combinations of different cutting speeds (50, 55, 60, and 65 m/min) and feed rates (0.063 and 0.08 mm/rev) to obtain training and testing data. The experimental results showed that the surface roughness (Ra) and roundness error (Re) values were obtained with the TiN monolayer- and TiAlN/TiN multilayer-coated drills, respectively. Using some of the experimental data in training stage, an ANN model was developed. To evaluate the performance of the developed ANN model, ANN predictions were compared with the experimental results. It was found that the determination coefficient values are more than 0.99 for both training and test data. Root mean square error and mean error percentage values were very low. ANN results showed that ANN can be used as an effective modeling technique in accurate prediction of the Ra and Re.     

Tribological properties of selected PVD coatings when slid against ductile materials

In this paper, a physical vapour deposited (PVD) deposited TiB₂ coating is compared in dry sliding with commercial PVD titanium nitride (TiN), titanium aluminium nitride (TiAlN) and titanium carbonitirde (TiCN) as to frictional properties and tendency of counter material pick-up. The aim is to investigate if the superior behaviour of the TiB₂ coating experienced in severe sliding applications against aluminium alloys can be extended to other materials with a similarly poor tribological characteristics.A new tribological test for sliding contact has been used. The test configuration involves two crossed elongated cylindrical test specimens which are forced to slide axially against each other at a constant sliding speed and a gradually increasing normal load, while recording the friction. The evaluation is performed by correlating the friction history with the width, topography and composition of the sliding tracks as detected by optical and scanning electron microscopy.Coated cemented carbide (CC) test cylinders have been slid against cylinders of a Ti alloy (Ti–6Al–4V), an Al alloy (Al 7075) and Inconel 718. It was shown that the TiB₂ surface displayed superior friction and anti-sticking properties, when tested against the aluminium alloy. Against the Ti and Inconel alloys no major difference between the coatings could be found. Instead, it is concluded that the friction coefficient is determined by the plastic properties of the counter material since a complete transfer layer instantly builds up on the coating.It proved possible to estimate the friction force from the width of the sliding tracks, the Vickers hardness of the counter material and simple plastic considerations. This estimation also verifies the unexpectedly low friction of all coatings against the Ti alloy.     

In vitro analysis of the wear,wear debris and biological activity of surface-engineered coatings for use in metal-on-metal total hip replacements

Extremely low wear rates have been reported for metal-on-metal total hip replacements, but concerns remain about the effects of metal ion release, dissolution rates and toxicity. Surface-engineered coatings have the potential to improve wear resistance and reduce the biological activity of the wear debris produced. The aim of this study was to examine the wear and wear debris generation from surface-engineered coatings: titanium nitride (TiN), chromium nitride (CrN) and chromium carbon nitride (CrCN) applied to a cobalt-chrome alloy (CoCr) substrate. The coatings were articulated against themselves in a simple geometry model. The wear particles generated were characterized and the cytotoxic effect on U937 macrophages and L929 fibroblasts assessed. The CrN and CrCN coatings showed a decrease in wear compared to the CoCr bearings and produced small (less than 40 nm in length) wear particles. The wear particles released from the surface engineered bearings also showed a decreased cytotoxic effect on cells compared to the CoCr alloy debris. The reduced wear volumes coupled with the reduced cytotoxicity per unit volume of wear indicate the potential for the clinical application of this technology.     

Monitoring of Wear Characteristics of TiN and TiAlN Coatings at Long Sliding Distances

TiN and TiAlN thin hard coatings have been widely applied on machine components and cutting tools to increase their wear resistance. These coatings have different wear behaviors, and determination of their wear characteristics in high-temperature and high-speed applications has great importance in the selection of suitable coating material to application. In this article, the wear behavior of single-layer TiN and TiAlN coatings was investigated at higher sliding speed and higher sliding distances than those in the literature. The coatings were deposited on AISI D2 cold-worked tool steel substrates using a magnetron sputtering system. The wear tests were performed at a sliding speed of 45 cm/s using a ball-on-disc method, and the wear area was investigated at seven different sliding distances (36–1,416 m). An Al₂O₃ ball was used as the counterpart material. The wear evolution was monitored using a confocal optical microscope and surface profilometer after each sliding test. The coefficient of friction and coefficient of wear were recorded with increasing sliding distance. It was found that the wear rate of the TiAlN coating decreases with sliding distance and it is much lower than that of TiN coating at longer sliding distance. This is due to the Al₂O₃ film formation at high temperature in the contact zone. Both coatings give similar coefficient of friction data during sliding with a slight increase in that of the TiAlN coating at high sliding distances due to the increasing alumina formation. When considering all results, the TiAlN coating is more suitable for hard machining applications.     

Experimental studies of the cutting force and surface morphology of explosively clad Ti–steel plates

The present work pertains to the study of clad material such as titanium plated steel in drilling process. The study was conducted for two types of indexable insert drills with different configuration of the tool coatings (TiAlN/AlTiN + TiN and TiAlN/TiN), the same geometry of insert and fixed machining conditions. Drilling process was assessed by the analysis of thrust force, torque and signal fluctuations of PSD function. In this context, surface morphology of the drilled holes and contact area was analysed. It has been observed that the use of the PSD function allows assessment of the drilling process in different layers of clad materials. Also was found that the parameters of the surface morphology are dependent upon the type of layers of the clad and the type of drill. Furthermore the reduction in torque results in obtaining smaller values of surface roughness parameter especially in the area of volume parameters of the bearing area curve.     

Study of wear resistance of thermal-diffusion boron nitride coatings on titanium

The wear resistance of commercially pure titanium VT1-0 covered with boron nitride coatings in pair with steel U8 is studied. It is found that the boron nitride coatings deposited from amorphous boron by thermal-diffusion saturation in molecular nitrogen at temperatures of 800?C850°C using the noncontact method improve the wear resistance of titanium during boundary sliding friction. Their characteristics are compared with those of boride coatings on titanium deposited by the same method. It is shown that the high-gradient strengthened layers formed during contact thermal-diffusion boronitriding within the 900?C950°C temperature range affect adversely the tribological performance of the boron nitride coating-steel pair.     

Abrasive wear behavior of high speed steel and hard metal coated with TiAlN and TiCN

The wear behavior of M2 high speed HSS steel and WC hard metal coated with TiAlN and TiCN were investigated and compared, using the pin on disk standard test with different loads. The coating PVD process has been done by two different suppliers, using an industrial equipment unit with optimized conditions. The coated layers were measured and characterized. The load, sliding distance and velocity of 0.5 m/s were kept constant during the abrasion test in order to control these variables. The counterface disks used were electric steel sheets from three different suppliers. The lost volume and temperature at the pin end have been measured during the wear test. Comparisons of tribological performance for the coated HSS and hard metal were done, using a plot of lost volume versus sliding distance for substrates and coatings. The pin worn surfaces were observed using a scanning electron microscope. A significant increase in the wear resistance of M2 steel and WC hard metal when coated with TiAlN and TiCN was observed. Quality of these coatings depended upon the supplier. Excessive porosity has diminished the TiAlN counting wear resistance from one supplier. However, in general the performance of TiAlN is superior to TiCN. The pin wear rate depended on the disk microstructure.     

Evaluation of the performance of coated carbide tools in face milling TC6 alloy under dry condition

Titanium and its alloys are well known as the typical different-to-cut materials because of their low thermal conductivity, high chemical reactivity, and low modulus of elasticity. During machining of titanium alloy, advanced high-speed, high-efficiency processing technologies are adopted to improve the production efficiency and reduce the production costs. The main goal of this work is to compare the performance of physical vapor deposition (PVD)-coated (TiN/TiAlN) and chemical vapor deposition (CVD)-coated (TiN/Al₂O₃/TiCN) carbide inserts in face milling TC6 alloy. To this end, the present paper reviewed the main works on the application of PVD- and CVD-coated tools in machining titanium alloys and the material performance of TC6 alloy, especially the machinability in machining process. Several tool life tests and tool wear experiments were carried out on a milling center with a five-axis spindle drive. Cutting forces were measured with a Kistler dynamometer. The failure modes and chip morphology were observed. Surface roughness and tool wear evolution were determined. The wear mechanism was discussed to compare the performance of PVD and CVD-coated tools. The main conclusions of this work were that the cutting tools made with PVD coating (TiN/TiAlN) had the excellent tooling quality and the main wear mechanisms were spalling and adhesion. PVD-TiN/TiAlN insert was more suitable to milling TC6 alloy than CVD-TiN/Al₂O₃/TiCN insert.     

Case Studies on Tribological Behavior of Coated Cutting Tools

Plasma surface engineering is a very promising way to enhance performance of metal cutting tools. The advantage of PVD coatings include increase the tool life, improve the roughness of machined surfaces, increase the cutting speed, etc.

This paper studied some new multiphase materials and multilayer structures of coatings based on TiN and TiC, ZrN, (Ti,Al)N,Al-Si-N. The change of contact conditions on cutting by coated tools, specific features of wear of tools with complicated geometry (like drills), effect of cutting conditions and workpiece materials on tribological behavior of indexable inserts during lathe turning and plain rotary were discussed.     

Arc Evaporation of Ti–Al–Ta–N Coatings: The Effect of Bias Voltage and Ta on High-temperature Tribological Properties

Recently, titanium aluminium tantalum nitride (Ti–Al–Ta–N) coatings have been shown to exhibit beneficial properties for cutting applications. However, the reason for the improved behaviour of these coatings in comparison to unalloyed Ti–Al–N is not yet clear. Here, we report on the tribological mechanisms present in the temperature range between 25 and 900 °C for this coating system, and in particular on the effect of the bias voltage during deposition on the tribological response. Based on these results, we provide an explanation for the improved performance of Ta-alloyed coatings. An industrial-scale cathodic arc evaporation facility was used to deposit the coatings from powder metallurgically produced Ti₄₀Al₆₀ and Ti₃₈Al₅₇Ta₅ targets at bias voltages ranging from −40 to −160 V. X-ray diffraction experiments displayed a change with increasing bias voltage from a dual-phase structure containing cubic and hexagonal phases to a single-phase cubic structure. Investigations of the wear behaviour at various temperatures showed different controlling effects in the respective temperature ranges. The results of dry sliding tests at room temperature were independent of bias voltage and Ta-alloying, where the atmosphere, i.e. moisture and oxygen, were the most important parameters during the test. At 500 °C, bias and droplet-generated surface roughness were identified to determine the tribological behaviour. At 700 and 900 °C, wear depended on the coating’s resistance to oxidation, which was also influenced by the bias voltage. In conclusion, Ta-alloyed coatings show a significantly higher resistance to oxidation than unalloyed Ti–Al–N which could be an important reason for the improved performance in cutting operations.     

Tribological performances of ZDDP and ashless triphenyl phosphorothionate (TPPT) as lubricant additives on Ti–N and Ti–Al–N coated steel surfaces

Abstract

In recent years, there has been much attention on the effects of lubricant additives on the friction and wear properties of surface coatings. However, little research has been conducted to investigate the influence of antiwear additives on the tribological performances of titanium nitride (Ti–N) and titanium aluminium nitride (Ti–Al–N) coatings. It has been reported that introducing aluminium into Ti–N coatings enhanced their oxidation resistance. In this study utilising a pin on cylinder tribometer, lubricants containing zinc dialkyl dithiophosphate (ZDDP) or a more environmentally friendly alternative, ashless triphenyl phosphorothionate (TPPT), were used. Experimental results revealed that ZDDP and TPPT helped to reduce wear on both coatings through the formation of a tribofilm, although it was also found that both additives increased the friction coefficient on both surfaces. Based on overall findings, this paper suggests the use of TPPT as a suitable ZDDP replacement for providing wear protection on Ti–N and Ti–Al–N coatings.     

Wear mechanisms and tool performance of TiAlN PVD coated inserts during machining of AISI 4140 steel

The tribological influences of PVD-applied TiAlN coatings on the wear of cemented carbide inserts and the microstructure wear behaviors of the coated tools under dry and wet machining are investigated. The turning test was conducted with variable high cutting speeds ranging from 210 to 410 m/min. The analyses based on the experimental results lead to strong evidences that conventional coolant has a retarded effect on TiAlN coatings under high-speed machining. Micro-wear mechanisms identified in the tests through SEM micrographs include edge chipping, micro-abrasion, micro-fatigue, micro-thermal, and micro-attrition. These micro-structural variations of coatings provide structure-physical alterations as the measures for wear alert of TiAlN coated tool inserts under high speed machining of steels.     

Investigation of the performance of carbide cutting tools with hard coatings in hard milling based on the response surface methodology

Machining of hard materials has become a great challenge for several decades. One of the problems in this machining process is early tool wear, and this affects the machinability of hard materials. In order to increase machinability, cutting tools are widely coated with nanostructured physical vapor deposition hard coatings. The main characteristics of such advanced hard coatings are high microhardness and toughness as well as good adhesion to the substrate. In this paper, the influence of hard coatings (nanolayer AlTiN/TiN, multilayer nanocomposite TiAlSiN/TiSiN/TiAlN, and commercially available TiN/TiAlN) and cutting parameters (cutting speed, feed rate, and depth of cut) on cutting forces and surface roughness were investigated during face milling of AISI O2 cold work tool steel (～61 HRC). The experiments were conducted based on 3¹³ factorial design by response surface methodology, and response surface equations of cutting forces and surface roughness were obtained. In addition, the cutting forces obtained with the coated and uncoated tools were compared. The results showed that the interaction of coating type and depth of cut affects surface roughness. The hard coating type has no significant effect on cutting forces, while the cutting force F _z is approximately two times higher in the case of uncoated tool.     

镍基合金喷熔层摩擦学行为与机制的研究

采用热喷熔工艺制备了两种镍基合金喷熔层,并选用高锰钢、不锈钢作为对比材料,研究了镍基合金喷熔层的摩擦磨损性能。研究结果表明：镍基合金喷熔层具有良好的耐磨损性能和较低的摩擦系数。镍含量对喷熔层的摩擦学性能有显著影响,高镍含量的镍基合金,其耐磨性能明显优于低镍含量的镍基合金。在低速轻载条件下,镍基合金喷熔层的磨损机理为微观犁削;高速重载时,表现为粘着磨损和磨料磨损,其中高镍含量的喷熔层表面形成了致密的转移膜,有效地降低了磨损率。     

Structural and tribological characterization of tungsten nitride coatings at elevated temperature

Transition metal nitrides exhibit excellent mechanical properties (hardness and Young's modulus), high melting point, good chemical stability and high electrical conductivity. However, tungsten nitrides still stand aside of the main attention. In our previous study, tungsten nitride coatings with different nitrogen content showed excellent wear resistance at room temperature. Nevertheless, many engineering applications require good tribological properties at elevated temperature. Thus, the present study is focused on the tribological behaviour (friction coefficient and wear rate) of tungsten nitride coatings at temperature up to 600 °C.

The structure, hardness, friction and wear of tungsten nitride coatings with nitrogen content in the range 30–58 at.% prepared by dc reactive magnetron sputtering were investigated. The tribological tests were performed on a pin-on-disc tribometer in terrestrial atmosphere with Al₂O₃ balls as sliding partner. The coating wear rate was negligible up to 200 °C exhibiting a decreasing tendency; however, the wear dramatically increased at higher temperatures. The coating peeled off after the test at 600 °C, which is connected with the oxidation of the coating.     

Low Friction CrNMPP/TiNDCMS Multilayer Coatings

Transition metal nitrides like CrN and TiN are widely used in automotive applications due to their high hardness and wear resistance. Recently, we showed that a multilayer architecture of CrN and TiN, deposited using the hybrid—high power impulse magnetron sputtering (HIPIMS) and direct current magnetron sputtering (DCMS)—HIPIMS/DCMS deposition technique, results in coatings which indicate not only increased mechanical and tribological properties but also friction coefficients in the range of diamond-like-carbon coatings when tested at RT and ambient air conditions. The modulated pulsed power (MPP) deposition technique was used to replace the HIPIMS powered cathode within this study to allow for a higher deposition rate, which is based on the complex MPP pulse configuration. Our results on MPP/DCMS deposited CrN/TiN multilayer coatings indicate excellent mechanical and tribological properties, comparable to those obtained for HIPIMS/DCMS. Hardness values are around 25 GPa with wear rates in the range of 2 × 10⁻¹⁶ Nm/m³ and a coefficient of friction around 0.05 when preparing a superlattice structure. The low friction values can directly be correlated to the relative humidity in the ambient air during dry sliding testing. A minimum relative humidity of 13% is necessary to guarantee such low friction values, as confirmed by repeated tests, which are even obtained after vacuum annealing to 700 °C. Our results demonstrate that the co-sputtering of high metal ion sputtering techniques and conventional DC sputtering opens a new field of applications for CrN/TiN coatings as high wear resistance and low friction coatings.