TiAlN Coatings Research Articles

Revealing wear mechanisms of coated shafts in low-speed journal bearings immersed in liquid Lead-Bismuth Eutectic (LBE)

This study investigates wear mechanisms of coated shafts in journal bearings within liquid lead-bismuth eutectic. Shafts were coated with TiAlN, a-C:H, multi-layer TiAlN with sputtered carbon, and chrome plating. Bearings made from sintered iron with carbon inclusions (DEVA 120 and DEVA 121) were tested in LBE at 200 °C and 50 rpm using a dedicated test rig. The a-C:H coatings failed due to tribofilm wear with DEVA 120, while TiAlN coatings failed from fatigue wear with DEVA 120 but succeeded with DEVA 121. Chrome-plated shafts experienced abrasive and adhesive wear with DEVA 121 but survived DEVA 120 due to transfer layer formation. The study highlights the need to understand wear mechanisms and material compatibility to develop durable coatings for harsh environments.

Evaluation of wear resistance of CrN, CrAlN, and TiAlN coatings deposited by multi-arc ion plating on spinning die of Cr12MoV

Abstract This study successfully deposited CrN, CrAlN, and TiAlN coatings on the surface of Cr12MoV substrate using multi-arc ion plating (MAIP). The influence of phase composition and surface morphology on the hardness, adhesion strength, friction performance, and wear mechanisms of these coatings was investigated, with a comparative analysis of their wear resistance. Nanoindentation results revealed that the hardness (H) of CrN, CrAlN, and TiAlN coatings increased by 70.37%, 74.97%, and 75.64%, respectively, compared to the substrate. The hardness (H) and elastic modulus (E) were found to be positively correlated. CrAlN demonstrated superior resistance to deformation, reflected in its higher H/E and H 3 /E 2 radios compared to the CrN and TiAlN. Adhesion tests showed that CrAlN had the strongest adhesion strength to the substrate, with an adhesion force of 81.55 N, representing a 14.78% and 8.46% improvement over CrN and TiAlN, respectively. Friction and wear tests identified CrAlN as having the lowest friction coefficient (0.389), attributed to its high hardness and strong adhesion. The wear mechanisms of CrAlN observed were primarily mild abrasive wear, oxidative wear, and adhesive wear. In comparison, CrN and TiAlN coatings exhibited higher friction coefficients of 0.424 and 0.391, respectively, due to their lower hardness and adhesion, which led to more severe oxidative and abrasive wear. Additionally, the TiAlN coating showed signs of brittle failure in wear scars, likely due to the formation of Al2O3 oxides during wear.

Effects of TiAlN Coating Thickness on Machined Surface Roughness, Surface Residual Stresses, and Fatigue Life in Turning Inconel 718

The surface roughness and surface residual stresses are affected by the coating thickness of physical vapor deposition (PVD) TiAlN tools, which could alter the service performance of machined components. However, the relationships among the tool coating thickness, the machined surface roughness, the surface residual stress, and the fatigue life are still not sufficiently illustrated. In this research, PVD TiAlN coatings with several thicknesses of 1.6 μm, 2 μm, 2.5 μm, and 3 μm were deposited on carbide tools. Turning experiments using Inconel 718 were conducted with uncoated and various TiAlN tools under flood cooling conditions. The surface roughness could be improved with the selection of thin PVD TiAlN coating thicknesses of 1.6 μm and 2 μm compared to that of uncoated tools. The tensile residual stresses at the machined surface in the directions of cutting speed and feed rate linearly decreased by 148.67% and exponentially decreased by 92.24% when the TiAlN coating thickness was increased from 0 μm to 3 μm. The values of the low-cycle fatigue life of machined Inconel 718 linearly increased by 15.60% with the increase in TiAlN coating thickness from 0 μm to 3 μm, which was mainly due to the improvement of surface residual stresses. The results could provide guidance for the selection of suitable TiAlN coating thicknesses for wet machining Inconel 718 based on the part service conditions.

Structures, electrochemical properties and corrosion mechanisms of TiAlCr(C)N/TiAlN/TiN coatings by DFT calculations

Element additions in ceramic coatings played a positive role in electrochemical corrosion process, and Cr and C were doped into TiAlN coating by cathode arc ion plating. The effects of Cr and C additions on the structures and electrochemical properties of TiAlN coatings in 3.5 % NaCl solution were comparatively investigated, and the corrosion mechanisms were discussed with the density functional theory calculation. The results show that the particle size of TiAlCrN/and TiAlCN/TiAlN/TiN coatings are 31.6 and 25.7 nm, respectively, and the corresponding bonding strength is 16.18 and 37.93 N, respectively. The corrosion resistance of TiAlCrN/TiAlN/TiN coating is higher compared with the TiAlCN/TiAlN/TiN coating, which is attributed to the stronger oxidation reactions of TiAlCrN/TiAlN/TiN coating. The donor density of passive film on the TiAlCrN/TiAlN/TiN coating is lower than that on the TiAlCN/TiAlN/TiN coating, showing the minor susceptibility of TiAlCrN/TiAlN/TiN coating to corrosion. Moreover, the band gap and DOS of Cr2N and Cr2O3 on the TiAlCrN/TiAlN/TiN coating are larger than those of Al3C4 on the TiAlCN/TiAlN/TiN coating, presenting the stronger corrosion resistance.

High-temperature tribological properties and wear mechanisms of multilayered cubic-BN/nanocrystalline diamond tool coatings

Wear failure of cutting inserts is the main form of failure that occurs when cutting difficult-to-machine materials at high speeds. To obtain cutting inserts with outstanding tribological properties, multilayered cubic boron nitride (cBN) and nanocrystalline diamond (NCD) coatings (cBN/NCD) were prepared on WC-6 wt% Co tool substrates. The tribological properties of the multilayered cBN/NCD coatings were studied at different temperatures, and the results showed that the coefficient of friction (COF) and wear rate of the coatings were closely interrelated to the temperatures, and the COF gradually decrease and the wear rate gradually increase as the temperature increased from room temperature (25 °C) to 600 °C. The COF and wear rate of the multilayer coatings at 600 °C were ∼0.05 and 8.43 × 10−6 mm3/(N⋅m), respectively. The wear resistance of the cBN/NCD coatings was higher than that of TiAlN coatings and PcBN tool materials by more than 3 and 4.5 times, respectively. The high-temperature wear failure modes of the multilayered cBN/NCD coatings were abrasive wear, diamond graphitization, and BN hydrolysis. Coating wear accelerated when pores were formed on the cBN surface of a multilayered cBN/NCD coating due to the low nucleation density of diamond. These results would guide the application of cBN/NCD-coated cutting tools in high-speed cutting processes.

Thermal stability and oxidation resistance of Ti0.22Al0.74Si0.04N coating synthesized by chemical vapor deposition

Addition of Si is known as an effective way to improve the thermal stability and oxidation resistance of TiAlN coatings. In this study, we focused on the thermal stability and oxidation resistance of a Ti0.22Al0.74Si0.04N coating which was deposited on cemented carbide substrate by low pressure chemical vapor deposition (LPCVD). According to X-ray diffraction (XRD), the phase composition of the as-deposited coating is composed of face-centered cubic (fcc-) TiN and wurtzite (w-) AlN. As the vacuum annealing temperature rises from 700 to 800 °C, the hardness increases and subsequently decreases as temperature further rises from 800 to 1100 °C, then remains basically unchanged above 1000 °C. At 900 °C and above, Co diffusion from the substrate into the coating is observed, which affects the mechanical properties of the coating. A maximum hardness of 35.6 ± 3.3 GPa is obtained after annealing in vacuum at 800 °C for 1 h. The results of transmission electron microscopy (TEM) indicate that the coating exhibits a structure similar to that of the deposited state after vacuum annealing at 1200 °C, consisting of nanocrystalline (Ti,Al)N embedded in amorphous SiNx. For the oxidation test, each sample was annealed in air with steps of 50 °C for 1 h within the range of 700–1000 °C. XRD and X-ray photoelectron spectroscopy (XPS) measurements demonstrate that the oxide layer is composed of rutile (r-) TiO2, amorphous SiO2 and a dominant amount of amorphous Al2O3 phase forms in the coating after annealing at 950 °C for 1 h. The coating exhibits excellent oxidation resistance with an oxide thickness of only 469 nm after annealing in air at 1000 °C for 1 h.

Tribological behaviour of TiAlN and AlCrN coatings on stainless steel

TiAlN and AlCrN coatings are widely used in applications that require high stress resistance. In this work, the tribological behaviour of physical vapour deposition (PVD) TiAlN and AlCrN commercial coatings deposited on AISI martensitic stainless steel is studied. Microstructure of the coatings was analysed by X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM) and nanohardness was measured. Pin-on-disk and abrasive wear tests were performed. Adhesion was evaluated using Rockwell C Indentation and scratch test. The thickness of both coatings was approximately 3 µm. AlCrN lost 30 and 10 times less volume than TiAlN in pin-on-disk tests, under low and high loads, respectively. The steady friction coefficient value was also lower. This indicated that the AlCrN coating had a better performance under sliding conditions. On the other hand, the mass loss was similar for both coatings under abrasive wear, even under severe conditions. In the scratch tests, TiAlN coating failed at 60 N load and AlCrN coating at 70 N, the latter showing a higher value of critical load. The deformation was similar for both coatings as it could be observed in the profiles obtained by a mechanical profilometer at 60 N, however, AlCrN did not show film delamination. This enhanced performance can be attributed to higher fracture toughness and load carrying capacity, which not only improved the mechanical properties of the coating but also its adhesion to the stainless-steel substrate.

Oxidation Resistance of TiAlN Coatings Deposited by Dual High-Power Impulse Magnetron Sputtering

Oxidation Resistance of TiAlN Coatings Deposited by Dual High-Power Impulse Magnetron Sputtering

Structure, mechanical and thermal properties of Ti1−x−y−zAlxTayBzN coatings

Multiple alloying is a preferred and practical approach to tailor the properties of TiAlN coatings. Here, we studied the structure, mechanical and thermal properties of Ti1−x−y−zAlxTayBzN coatings by cathodic arc evaporation. Increasing Ta content causes a structural transition from mixed cubic and wurtzite Ti0.35Al0.54Ta0.03B0.08N, Ti0.35Al0.54Ta0.05B0.06N, and Ti0.34Al0.52Ta0.09B0.05N to cubic Ti0.33Al0.51Ta0.13B0.03N and Ti0.33Al0.50Ta0.15B0.02N. This structural change causes an increased hardness, where the maximum hardness of 38.0 ± 0.8 GPa is obtained by Ti0.33Al0.51Ta0.13B0.03N. The cubic Ti0.33Al0.51Ta0.13B0.03N and Ti0.33Al0.50Ta0.15B0.02N coatings reveal higher hardness during the whole annealing range, which reach the peak hardness of 39.3 ± 0.9 and 36.7 ± 1.0 GPa at 1000 °C, respectively. In addition, the oxidation resistance of Ti1-x-y-zAlxTayBzN coatings is closely related to the Ta content. After oxidation of 10 h at 1000 °C, the oxide scale of Ti0.35Al0.54Ta0.05B0.06N, Ti0.34Al0.52Ta0.09B0.05N, Ti0.33Al0.51Ta0.13B0.03N, and Ti0.33Al0.50Ta0.15B0.02N are ∼2.31, ∼1.44, ∼1.23, and ∼ 1.08 μm, respectively, while Ti0.35Al0.54Ta0.03B0.08N has been entirely oxidized.

Strain and phase evolution in TiAlN coatings during high-speed metal cutting: An in operando high-energy x-ray diffraction study

We report on phase and strain changes in Ti1-xAlxN (0 ≤ x ≤ 0.61) coatings on cutting tools during turning recorded in operando by high-energy x-ray diffractometry. Orthogonal cutting of AISI 4140 steel was performed with cutting speeds of 360–370 m/min. Four positions along the tool rake face were investigated as a function of time in cut. Formation of γ-Fe in the chip reveals that the temperature exceeds 727 °C between the tool edge and the middle of the contact area when the feed rate is 0.06 mm/rev. Spinodal decomposition and formation of wurtzite AlN occurs at the positions of the tool with the highest temperature for the x ≥ 0.48 coatings. The strain evolution in the chip reveals that the mechanical stress is largest closest to the tool edge and that it decreases with time in cut for all analyzed positions on the rake face. The strain evolution in the coating varies between coatings and position on the rake face of the tool and is affected by thermal stress as well as the applied mechanical stress. Amongst others, the strain evolution is influenced by defect annihilation and, for the coatings with highest Al-content (x ≥ 0.48), phase changes.

Improved mechanical and tribological properties of TiAlN coatings by high current pulsed electron beam irradiation

High current pulsed electron beam (HCPEB) irradiation is an important surface engineering technique, which has been proved to be valid in modifying the surface microstructure and properties of various materials. In this work, HCPEB was employed to irradiate TiAlN coatings. The microstructure, mechanical and tribological properties of both original and irradiated TiAlN coatings were investigated. The results showed that the surface roughness of the TiAlN coatings first increased with 5 pulses of HCPEB irradiation, and then gradually declined with a further increase in pulse numbers. Compared with the original coating, the coating irradiated by 15 pulses demonstrated superior hardness (up to 33.4 GPa) and adhesion strength (112N), excellent wear resistance (wear rate of 3.3 × 10−6 mm3/Nm) and low friction coefficient (0.37). It is believed that the grain refinement, formation of the transition zone and adjustment of residual stresses after 15 pulses of HCPEB treatment are responsible for the improvement in both mechanical and tribological properties of the TiAlN coatings. These findings might suggest the potential applications of HCPEB irradiation for surface modification and hardness improvement of hard nitride coatings.

Tribological Behavior of Physical Vapor Deposition Coating for Punch and Dies: An Overview

Punches and dies are cutting tools used to make holes on metallic surfaces using the punch which passes through the work into a die. Todays tool/die machinists and buyers need to know more than simply the qualities of the raw metal that forms the tooling blank because of the rapid evolution of PVD coating technology. When it comes to tooling design, raw material, heat treatment, coating qualities, material being machined, cycle time requirements and permitted machine downtime, they must comprehend the full system. Surface modifications for punch/dies are typically required to improve their mechanical and corrosion, properties. Therefore PVD coatings of punch/die material using TiN, TiCN, CrN, TiAlN and nanocomposite coatings has improved the tribological properties, reduce total cost of tools and down time. This paper focuses on comprehensive review on PVD processes on punch/die materials, properties of die materials such as wear, hardness and surface finishes etc. In addition to that coating materials, its properties and characterization techniques were addressed.

Influence of Si addition on the phase structure and oxidation behavior of PVD AlTiN and AlTiCrN coatings using high-resolution characterization techniques

The influence of Si concentrations on AlTiN and AlTiCrN coatings deposited by PVD has been investigated by using high-resolution characterization techniques: TEM, Dynamic SIMS, Atom Probe Tomography (APT) analyses and nano hardness measurements. First, investigations focus on crystallographic phase stability, microstructural observations and micromechanical studies to understand the effect of the Si addition on these two nitride coatings. Second, the oxidation mechanisms and the kinetics of oxide growth at 950 °C for various durations are examined. Results indicate that the addition of Si introduces high compressive stresses in both coating groups, reaching values in the range of − 6 GPa. However, the behavior of Si content differs for AlTiN coatings with and without chromium. In AlTiSiN coatings, increasing Si addition leads to reduce residual stresses, while no significant change is observed for AlTiCrSiN coatings. This stress evolution is associated with a decrease in crystallinity density of the TiAlN coatings due to Si addition, but this structural phenomenon is not observed when Si is added to the quaternary metallic coatings TiAlCrN. Si content also influences the nanohardness, but the variation among coating is not substantial, with values around 34 + /− 2 GPa, and an elastic-modulus around 443 + /− 40 GPa. Regarding oxidation resistance at 950 °C, the addition of Si in AlTiN coating results in the formation of an external alumina oxide layer and beneath it, a nanometer sized TiO2 anatase crystallites layer. After the growth of this bi-layer oxide scale, the inward cationic diffusion of the oxygen is very significantly reduced, and it can explain its high oxidation resistance. In contrast, for AlTiCrSiN coatings, the oxide scale morphology is different, consisting of a pure TiO2rutile outer layer, followed by an Al-rich oxide and a mixed oxide region of (AlCr)2O3 with small islands of TiO2. The growth of this last oxide scale shows a regular increase over time, primarily driven by inward oxygen diffusion at the nitride coating interface.

Tribological and Mechanical Properties of Nanocrystalline TiN, TiAlN, and TiSiN PVD Coatings

Tribological and Mechanical Properties of Nanocrystalline TiN, TiAlN, and TiSiN PVD Coatings

Capability Analysis of AZ91D Magnesium Alloy Precision Milling Process with Coated Tools.

Process capability analysis is the main tool of statistical process control. It is used for the ongoing monitoring of product compliance with imposed requirements. The main objective and novelty of the study were to determine the capability indices for a precision milling process of AZ91D magnesium alloy. Machining was performed in terms of variable technological parameters and using end mills with protective TiAlN and TiB2 coatings intended for the machining of light metal alloys. The Pp and Ppk process capability indices were determined based on the measurements of the dimensional accuracy of the shaped components that were taken on a machining centre with a workpiece touch probe. Obtained results demonstrated that the type of tool coating and variable machining conditions had a significant impact on the machining effect. The selection of appropriate machining conditions enabled a terrific level of capability to be achieved at a tolerance of 12 µm, several times lower than under unfavourable conditions where the tolerance was up to 120 µm. Improvements in process capability are mainly achieved by adjusting the cutting speed and feed per tooth. It was also shown that process estimation based on improperly selected capability indices might lead to an overestimation of the actual process capability.

Adhesive wear of TiAlN coatings during low speed turning of stainless steel 316L

The wear behavior of TiAlN coatings during turning of stainless steel 316L at low cutting speeds (60–120 m/min) was investigated using scanning electron microscopy. In this speed range, the coatings fail by fracture due to an adhesive wear mechanism. The fracture of the coating is described in detail, including the strong influence of Al-content and cutting speed on the rate of wear. Low Al-content (x ≤ 0.23) coatings showed worse wear resistance than high Al-content (x ≥ 0.53) samples. Less substrate is exposed when the cutting speed is increased, because of reduced adhesive wear. The TiN and Ti0.77Al0.23N coatings are severely worn for all cutting speeds while Ti0.47Al0.53N and Ti0.38Al0.62N remain essentially unaffected at the highest speed. The difference in wear behavior is interpreted as a difference in the fracture toughness of the coatings.

Influence of Si and Ta mixed doping on the structure, mechanical and thermal properties of Ti[sbnd]Al[sbnd]N coatings

Alloying with Si or Ta is an effective method to upgrade the properties of TiAlN coatings. In the present work, we prepared Ti0.54Al0.46N, Ti0.46Al0.45Si0.09N as well as Ti0.42Al0.43Si0.09Ta0.06N coatings, and then investigated the effect of Si and Ta mixed doping on the structure, mechanical and thermal properties of TiAlN coatings. The hardness of cubic Ti0.54Al0.46N coating is 28.6 ± 0.9 GPa, whereas the mixed cubic and wurtzite Ti0.46Al0.45Si0.09N coating presents a higher hardness of 29.1 ± 1.1 GPa. The Si and Ta mixed doping leads to a maximum hardness of 34.1 ± 0.8 GPa for cubic Ti0.42Al0.43Si0.09Ta0.06N coating. The thermal stability of TiAlN coatings is more beneficial from the Si and Ta mixed doping. After annealing at 1100 °C, the Ti0.42Al0.43Si0.09Ta0.06N coating reaches a peak hardness of 37.9 ± 1.1 GPa due to the age-hardening effect from the spinodal decomposition, whereas the hardness of Ti0.54Al0.46N and Ti0.46Al0.45Si0.09N coatings decrease to 30.4 ± 1.3 and 32.9 ± 0.9 GPa, respectively. Furthermore, the Ti0.42Al0.43Si0.09Ta0.06N coating shows the best oxidation resistance. After oxidation at 1000 °C for 15 h, the oxide scale thickness of Ti0.42Al0.43Si0.09Ta0.06N is only ∼0.56 μm, whereas ∼0.91 μm thick oxide scale is formed on the Ti0.46Al0.45Si0.09N coating.

Energy Flux at the Substrate During Dual Magnetron Sputtering of TiAlN Coating

Energy Flux at the Substrate During Dual Magnetron Sputtering of TiAlN Coating

Properties of TiAlN Coatings Obtained by Dual-HiPIMS with Short Pulses

The paper focuses on the dual high-power impulse magnetron sputtering of TiAlN coatings using short pulses of high power delivered to the target. The surface morphology, elemental composition, phase composition, hardness, wear resistance, and adhesive strength of TiAlN coatings with different Al contents were investigated on WC-Co substrates. The heat resistance of the TiAlN coating was determined with synchrotron X-ray diffraction. The hardness of the TiAlN coating with a low Al content ranged from 17 to 30 GPa, and its wear rate varied between 1.8∙10-6 and 4.9∙10-6 mm3·N-1·m-1 depending on the substrate bias voltage. The HF1-HF2 adhesion strength of the TiAlN coatings was evaluated with the Daimler-Benz Rockwell C test. The hardness and wear rate of the Ti0.61Al0.39N coating were 26.5 GPa and 5.2∙10-6 mm3·N-1·m-1, respectively. The annealing process at 700 °C considerably worsened the mechanical properties of the Ti0.94Al0.06N coating, in contrast to the Ti0.61Al0.39N coating, which manifested a high oxidation resistance at annealing temperatures of 940-950 °C.

Comparative Characterization of the TiN and TiAlN Coatings Deposited on a New WC-Co Tool Using a CAE-PVD Technique

The main objective of this work was to assess and compare the structure and mechanical properties of the TiN and TiAlN coatings deposited on a new WC-Co tool using the cathodic arc evaporation vacuum deposition (CAE-PVD) technique. The cutting tool was sintered at high temperature and high pressure using a powder tungsten carbide matrix ligated with cobalt (WC-Co). Powdered grain growth inhibitors (TiC, TaC, and NbC) were admixed into the matrix to enhance its strength and to facilitate the adhesion of the Ti base coatings. Detailed scanning electron microscopy with energy-dispersive spectrometry (SEM-EDS) and X-ray diffraction (XRD) analyses were performed, aiming to substantiate the effectiveness of the inhibitor additions. XRD data were thoroughly exploited to estimate the phase contents, average crystallite sizes (D), coating thicknesses (t), texture coefficients (Thkl), and residual stress levels (σ). Atomic force microscopy (AFM) was used to calculate the average roughness (Ra) and the root mean square (Rq). The microhardness (µHV) was measured using the Vickers method. The TiAlN characteristics (D = 55 nm, t = 3.6 μm, T200 = 1.55, µHV = 3187; σ = −2.8 GPa, Ra = 209 nm, Rq = 268 nm) compared to TiN ones (D = 66 nm, t = 4.3 μm, T111 = 1.52, µHV = 2174; σ = +2.2 GPa, Ra = 246 nm, Rq = 309 nm) substantiate the better adequacy of the TiAlN coating for the WC-Co substrate. The structural features and data on the TiN and TiAlN coatings, the tool type, the different stress kinds exerted into these coatings, and the way of discrimination of the coating adequacy are the novelties addressed in the paper.