Physical Vapor Deposition Coatings Research Articles

Development of surface coatings for high-strength low alloy steel filler wires and their effect on the weld metal microstructure and properties

The lightweight construction of steel structures is often limited by the mechanical properties of the weld metal. The strength values of modern base materials are not achieved in the weld metal. There is a considerable need to develop welding consumables that allow the processing of modern fine-grained structural steels without limiting their potential. The Physical Vapor Deposition (PVD) coating of welding wire electrodes can increase the strength of the weld metal of a Mn4Ni2CrMo welding wire electrode by up to 30%. By using different coating elements, the Hall–Petch relationship can be exploited and such an increase in strength can be achieved. Especially by applying titanium, vanadium, and yttrium coatings, the strength of the weld metal can be increased. Due to a multilayer structure of the coating, the weld metal and the process can be influenced independently of each other. The effects of mono-element coatings and multi-component coatings on the weld metal and the process are discussed. PVD coatings allow welding wire electrodes to be individually adapted to the requirements.

High temperature tribological behaviour of PVD coated tool steel and aluminium under dry and lubricated conditions

Aluminium alloys are commonly used as lightweight materials in the automotive industry. This non-ferrous family of metallic alloys offers a high versatility of properties and designs. To reduce weight and improve safety, high strength-to-weight ratio alloys (e.g. 6XXX and 7XXX), are increasingly implemented in vehicles. However, these alloys exhibit low formability and experience considerable springback during cold forming, and are therefore hot formed. During forming, severe adhesion (i.e. galling) of aluminium onto the die surface takes place. This phenomenon has a detrimental effect on the surface properties, geometrical tolerances of the formed parts and maintenance of the dies. The effect of surface engineering as well as lubricant chemistry on galling has not been sufficiently investigated. Diamond-like carbon (DLC) and CrN physical vapour deposition (PVD) coated steel have been studied to reduce aluminium transfer. However, the interaction between lubricants and PVD coatings during hot forming of aluminium alloys is not yet fully understood. The present study thus aims to characterise the high temperature tribological behaviour of selected PVD coatings and lubricants during sliding against aluminium alloy. The objectives are to first select promising lubricant-coating combinations and then to study their tribological response in a high-temperature reciprocating friction and wear tester. Dry and lubricated tests were carried out at 300 °C using a commercial polymer lubricant. Tests using DLC, CrN, CrTiN, and CrAlN coated tool steel were compared to uncoated tool steel reference tests. The initial and worn test specimen surfaces were analysed with a 3-dimensional (3D) optical profiler, scanning electron microscope (SEM) and energy dispersive X-ray spectroscope (EDS) as to understand the wear mechanisms. The results showed formation of tribolayers in the contact zone, reducing both friction and wear. The stability of these layers highly depends on both the coatings’ roughness and chemical affinity towards aluminium. The DLC and CrN coatings combined with the polymer lubricant were the most effective in reducing aluminium transfer.

Blunting of the Cutting Edges of Hard-Alloy Mills and PVD Coating Application

The life of hard-alloy end mills with blunting of the cutting edge is compared in the presence and absence of a TiAlN PVD coating. The workpiece considered is VT6 titanium alloy; the coating is applied on an Eifeler Alpha 400p system. On that basis, a method is proposed for extending the life of monolithic mills with a PVD (physical vapor deposition) coating, by optimizing the blunting of the cutting edge.

The Use of Chromium and Chromium (III) Oxide PVD Coatings to Resist the Corrosion Driven Coating Delamination of Organically Coated Packaging Steel

This paper describes a systematic study into the role of chromium and chromium (III) oxide thickness in preventing corrosion driven coating disbondment of organically coated packaging steel. A graded wedge of chromium and chromium (III) oxide is applied to steel using physical vapour deposition (PVD). A polyvinyl butyral (PVB) overcoat is applied and corrosion is initiated from an artificial defect using NaCl. Scanning Kelvin probe (SKP) potentiometry is used to monitor coating delamination. Wedge thickness variation allows for high throughput investigations into the effect of both metallic chromium and chromium (III) oxide thickness, on coating disbondment rate. A linear reciprocal relationship is observed between chromium metal thickness and disbondment rate. Increasing chromium (III) oxide thickness (applied over chromium metal) results in a decrease in delamination rate. This work highlights the ability of PVD to produce chromium/chromium (III) oxide corrosion resistant coatings to use as alternatives to hexavalent chromium-based systems.

A systematic study of β-type Ti-based PVD coatings on magnesium for biomedical application

A non-toxic and non-allergic β-type Ti–29Nb–13Ta-4.6Zr (hereafter abbreviated as TNTZ) target material was prepared by the vacuum arc-melting process and then hot-forged, successfully. The TNTZ target has been deposited on the pure magnesium (Mg) and AZ31 Mg alloys by the physical vapor deposition (PVD) method. The characterization of the coatings was carried out by using SEM, EDS, AFM, and XRD techniques. The coating adhesion and its hardness were determined by scratch and Vickers tests, respectively. The corrosion resistance of the coatings was analyzed in simulated body fluid (SBF) under in-vitro conditions. Also, the coating wettability was compared by contact angle measurements. The results showed that the coatings had a very dense columnar and compact microstructure. The grain sizes were calculated between 20 and 40 nm, and the porosity of the coating was about 8.5% (±1.5). The hydrophilicity of the Ti-based PVD coating was better than the uncoated Mg. The failure mechanism of the coating during the scratch test was formed as conformal cracks. The in-vitro corrosion tests indicated that the Ecorr values of the TNTZ coated pure Mg and AZ31 alloy were nobler about 400 mV than the uncoated Mg-based samples. At the intensive stage of the corrosion, remarkable corrosion products, grown pits, and deep cracks were also observed on TNTZ-based coating layers due to the heavy corrosion attacks in SBF.

Resistance of PVD Coatings to Erosive and Wear Processes: A Review

Due to the increasing maintenance costs of hydraulic machines related to the damages caused by cavitation erosion and/or erosion of solid particles, as well as in tribological connections, surface protection of these components is very important. Up to now, numerous investigations of resistance of coatings, mainly nitride coatings, such as CrN, TiN, TiCN, (Ti,Cr)N coatings and multilayer TiN/Ti, ZrN/CrN and TN/(Ti,Al)N coatings, produced by physical vapor deposition (PVD) method using different techniques of deposition, such as magnetron sputtering, arc evaporation or ion plating, to cavitation erosion, solid particle erosion and wear have been made. The results of these investigations, degradation processes and main test devices used are presented in this paper. An effect of deposition of mono- and multi-layer PVD coatings on duration of incubation period, cumulative weight loss and erosion rate, as well as on wear rate and coefficient of friction in tribological tests is discussed. It is shown that PVD coating does not always provide extended incubation time and/or improved resistance to mentioned types of damage. The influence of structure, hardness, residence to plastic deformation and stresses in the coatings on erosion and wear resistance is discussed. In the case of cavitation erosion and solid particle erosion, a limit value of the ratio of hardness (H) to Young’s modulus (E) exists at which the best resistance is gained. In the case of tribological tests, the higher the H/E ratio and the lower the coefficient of friction, the lower the wear rate, but there are also many exceptions.

Thin-Film PVD Coating Metamaterials Exhibiting Similarities to Natural Processes under Extreme Tribological Conditions.

This paper discusses the surface-engineered nanomaterials (adaptive nano-structured physical vapor deposition (PVD) thin-film coatings) that can effectively perform under severely non-equilibrium tribological conditions. The typical features of these nanomaterials are: (a) Dynamically interacting elements present in sufficient amounts to account for its compositional/structural complexity; (b) an initial non-equilibrium state; (c) optimized micro-mechanical characteristics, and (d) intensive adaptation to the external stimuli. These could be considered as functionally graded nanomaterials that consist of two major layers: an underlying (2–3 microns) thin-film PVD coating, the surface on which an outer nanoscale layer of dynamically re-generating tribo-films is produced as a result of self-organization during friction. This tribo-film nanolayer (dissipative structures) was discovered to represent complex matter, which exhibits characteristic properties and functions common to naturally occurring systems. These include adaptive interaction with a severely non-equilibrium environment; formation of compounds such as sapphire, mullite, and garnet, similar to those that arise during metamorphism; ability to evolve with time; as well as complexity and multifunctional, synergistic behavior. Due to several nanoscale effects, this nanolayer is capable of protecting the surface with unprecedented efficiency, enabling extensive control over the performance of the entire surface-engineered system. These surface-engineered nanomaterials can achieve a range (speed and level) of adaptability to the changing environment that is not found in naturally occurring materials. Therefore, these materials could be classified as metamaterials. The second major characteristic of these materials is the structure and properties of the coating layer, which mostly functions as a catalytic medium for tribo-film generation and replenishment. A functioning example of this type of material is represented by an adaptive hard thin-film TiAlCrSiYN/TiAlCrN nano-multilayer PVD coating, which can efficiently work in an extreme environment, typical for the dry machining of hard-to-cut materials.

High-energy X-ray phase analysis of CMAS-infiltrated 7YSZ thermal barrier coatings: Effect of time and temperature

Abstract

Controllable preparation of micro-textures on WC/Co substrate surface by an integrated laser-dry etching process for improving PVD coatings adhesion

The micro-texture fabricated on the substrate surface of coatings is an established method for enhancing the Physical Vapor Deposition (PVD) coatings adhesion. Currently, laser micromachining is widely used to prepare the micro/nano-texture. Nevertheless, it has a problem of low processing accuracy, such as irregular texture edges and irregular protrusions inside the textures. Here, we propose an ion beam etching (IBE)-assisted laser machining approach to fabricate micro-texture, and the effect of IBE/laser textures on the PVD coatings adhesion is revealed for the first time. The profile evolution mechanism of the micro-textures on the cemented carbide during etching process was investigated. By IBE-assisted laser machining, a ring-shaped microholes array with high precision and controllability was fabricated on the cemented carbide substrate surface. Then, the textured substrates were coated with TiAlN materials using cathode arc-evaporation technique. The scratch tests and dry wear tests on the coatings with the textured substrates were carried out, demonstrating that the IBE/laser textured coatings exhibited higher adhesive strength compared to that of the untextured and laser textured ones. Thus, the IBE-assisted laser machining shows a great potential in the preparation of high precision micro-textures for enhancing PVD coatings adhesion.

Preparation of micro-textures on cemented carbide substrate surface by plasma-assisted laser machining to enhance the PVD tool coatings adhesion

The micro-texture fabricated on the substrate surface of coatings is an established method for enhancing the Physical Vapor Deposition (PVD) coatings adhesion. Currently, laser micromachining is widely used to prepare the micro-texture. Nevertheless, it suffers from the problem of low fabrication quality, such as irregular texture edges and irregular protrusions inside the textures. Meanwhile, to achieve sufficient coating adhesion, the improvement of physical-chemical bonding between coatings and substrate is crucial. Here, we propose a plasma-assisted laser machining approach to fabricate micro-texture, and the effect of plasma/laser textures on the interfacial properties of PVD tool coatings, especially the physical-chemical bonding interfaces is revealed for the first time. The micro-topography, chemical structure and wettability of the plasma/laser textured substrate surface were investigated. The scratch tests on the coatings with different pretreated substrates and dry cutting experiments of stainless steel were carried out. Results show that the plasma/ laser textured substrate was conducive to coatings in terms of wettability, phase composition, roughness and hardness, and specific surface area, which could enhance the interfacial properties of PVD coatings. Thus, the critical load of plasma/laser textured coatings (FN, C2 = 103 N) exhibited higher values compared to that of the untextured one (FN, C2 = 70 N), and an obviously reduction in cutting force of FX up to 34.82 %, FY up to 36.15 %, FZ up to 27.71 % by plasma/laser textured coated tool was achieved. Furthermore, the mechanisms for the effects of plasma/laser textures on the coating adhesion were discussed.

Corrosion and wear behavior of TiN PVD coated 304 stainless-steel

Ti/TiN multilayered physical vapor deposition (PVD) coatings were deposited on stainless-steel by cathodic arc deposition method. Bare sample of stainless steel 304 was compared with monolithic TiN coating and TiN coating having 2, 4, 6 and 8 Ti interlayers. The properties like corrosion and wear resistance were studied and analyzed comparatively. Potentiodynamic polarization curves showed that highest corrosion resistance was indicated by TiN coating with 8 Ti interlayers. Sample having 8 Ti interlayers have high corrosion potential (Ecorr) and low corrosion current density (Icorr) as compared to other samples. This may be attributed to the arrangement of interlayers that prevents the corrosive agents to penetrate surface. All multi-layered coatings show better results than the substrate material. Pin on disk wear test revealed that coating having monolithic TiN layer have the lowest coefficient of friction and consequently have less wear volume and wear rate as compared to other coatings with Ti interlayers. These results made the investigated coated stainless steel 304 valuable for wide range of industrial applications that required wear and corrosion resistance.

Analysis of the Impact of Hard PVD Coatings on the Abrasion Resistance of the Compressor Blades

The article deals with the application of PVD (Physical Vapour Deposition) coatings onto the surface of compressor blades. In sandy or dusty conditions, compressor blades are the first obstacle for particles which are being sucked into the jet engine. Compressor blades equipped with a protective layer should have greater resistance against erosive and abrasive damage. To support this theory, an empirical experiment had to be conducted. Based on the data acquired from the experiment, we were able to summarise the effectiveness of coatings applied.

Research on Tribological Characteristics of Hard Metal WC-Co Tools with TiAlN and CrN PVD Coatings for Processing Solid Oak Wood

The article presents research results that demonstrate the impacts of mechanical and tribological characteristics on the efficiency of cutting tools made from hard metal WC-Co. Uncoated tools and tools coated with physical vapor deposition (PVD) coatings (CrN and TiAlN) were tested. The thickness of coatings was determined, and tests of roughness, microhardness, and adhesion were performed. The coefficient of friction (COF) was established by different methods, and the wear of the tested cutters which occurs during the milling of solid oak wood, and the impact of this on surface roughness, were determined. The results revealed that uncoated WC-Co cutters are the least resistant to wear, while cutters coated with chromium nitride (CrN) are the most resistant. Both PVD coatings were damaged in the 9050 m in area of the cutting edge.

Surface Treatments Solutions to Green Tribology

The objective of this paper is to highlight the need to combine lifecycle environmental assessment with durability evaluation (tribology and engine tests) to evaluate the potential of surface technologies to contribute to the green deal, in order to make Europe the first climate-neutral continent. Tribology is a scientific discipline that allows one to understand the system reaction to friction and wear. Tribological testing machines are prepared to measure friction at the laboratory level to minimize the wear and heat dissipation of two bodies in relative movement, thus improving the energy efficiency and minimizing CO2 emissions. In this paper, different surface technologies, such as high-velocity oxyfuel (HVOF), physical vapor deposition (PVD), and clean Cr electrolytic processes, are analyzed as promising surface technology solutions from both performance and environmental impact perspectives to replace harmful Cr(VI) coatings. The tribology simulates the working conditions of the real system at the laboratory level, reproducing the failure mechanism and facilitating the laboratory screening of the energy efficiency and durability of materials solutions for certain tribological systems—in this case, engine components. The tribological test results give information about the behavior of materials, while the engine tests gives information about the behavior of components. In this paper, the environmental impact of the production process of the coatings is also analyzed. Two hard chrome processes are compared, demonstrating that by controlling the production process it is possible to significantly reduce the environmental impact of the chrome-plated process, minimizing the environmental impact to that of PVD coatings. The environmental impact of the tested HVOF process is lower than traditional Cr(VI)-plated coatings but higher than PVD coatings. Combining the information from the lifecycle assessment (LCA) and tribological studies, it is possible to assess both the performance and the environmental impact of the surface treatments. This methodology is a tool to that can be used minimize CO2 emissions at the design phase to improve the energy efficiency of products and processes.

Investigation of PVD thin films as hydrogen barriers in aluminized press hardened steels (PHS)

The reduction of hydrogen intake of aluminized boron press hardened steel Usibor®1500 during austenitisation at 900 °C under N2 humid atmosphere has been explored by applying thin physical vapour deposition (PVD) coatings. A wide range of metallic coatings have been explored including Au, Cu, Ti, Y, Mo, W, Cr, Ni, Ni0.8Cr0.2, Ni0.4Cr0.6, Inconel 690 and stainless steel 316L as well as some nitrides WN, CrN and oxides Al2O3 and SiO2. W, Y and Ti enhance the increase of hydrogen intake, SiO2 and Al2O3 have no effect while Au, Cu, Mo, CrN, WN, Cr, Ni and NiCr alloys provide a decrease of the hydrogen ingress. The barrier effects of these coatings are discussed as a function of their thicknesses and chemical composition of the NiCr coatings. The most efficient barrier to hydrogen intake is obtained in this study for Ni0.8Cr0.2 coating with a reduction higher than 50% for an optimum coating thickness of 200 nm. The structure and the surface of the latter coating are investigated after austenitisation by a combination of techniques.

Experimental Study of the Influence of Deposition of Multilayer CrN/CrCN PVD Coating on Austenitic Steel on Resistance to Cavitation Erosion

The impact of deposition of multilayer CrN/CrCN coating on X6CrNiTi18-10 steel by means of the PVD (physical vapour deposition) method on resistance to cavitation erosion has been investigated. Cavitation tests were performed using a cavitation chamber with a barricade system at the inlet pressure p1 = 600 kPa and the outlet pressure p2 = 123 kPa. Deposition of CrN/CrCN coating allowed increasing duration of the incubation period and decreasing cumulative volume loss until 500 min of exposure. The erosion of the CrN/CrCN–X6CrNiTi18-10 system begins with the removal of microdroplets from the coating surface and surface undulation. The surface undulation increases with the exposure time leading to coating fracture in a brittle mode. Initiation sites of cracks were located inside the PVD coating. Measurements of surface roughness illustrate uneven degradation of the exposed surface and the location of slight and severe erosion zones. The Ra parameters obtained for the CrN/CrCN–X6CrNiTi18-10 system and X6CrNiTi18-10 steel after 180 min of erosion were comparable. An elongation of erosion test up to 600 min resulted in a higher increase in surface roughness of the CrN/CrCN coating–X6CrNiTi18-10 steel system in comparison to that of X6CrNiTi18-10 steel. With increasing exposition time, the rate of increase of the surface roughness decreased due to overlapping damage.

The influence of residual stress on the properties and performance of thick TiAlN multilayer coating during dry turning of compacted graphite iron

TiAlN is one of the most widely used physical vapour deposition (PVD) coatings in the manufacturing industry. Naturally, the performance of this coating is dependent on its properties, which can be tuned and optimized according to the application. Residual stress is one of the properties which affects hardness, fracture toughness, and adhesion of the coating. Although it is difficult to make a general recommendation for desirable residual stress values, individual recommendations can be made based on a specific workpiece material and tool wear mechanism. In this regard, adhesion wear and the formation of built-up edge were identified as the dominant wear mechanism during dry turning of compacted graphite iron and a coating's residual stress should be adjusted to minimize the damage from adhesion wear. Therefore, the present work investigates cutting performance and related coating properties of multilayer thick TiAlN coatings with different residual stress designs. For this purpose, residual stress was adjusted by varying the substrate bias voltage during the deposition process. The effect of residual stress on properties such as hardness, yield strength, and adhesion were studied by nanoindentation and scratch tests. Moreover, the dominant wear pattern, especially on the rake face and cutting edge, was thoroughly studied using a scanning electron microscope (SEM). The results showed increased mechanical properties such as hardness and yield strength with higher substrate bias voltages and therefore higher residual stresses. However, the coating with the lowest compressive residual stress outperformed the other coatings during machining due to a combination of high adhesion to the substrate and low as-deposited defects which effectively delayed cutting-edge exposure.

Review of Growth Defects in Thin Films Prepared by PVD Techniques

The paper summarizes current knowledge of growth defects in physical vapor deposition (PVD) coatings. A detailed historical overview is followed by a description of the types and evolution of growth defects. Growth defects are microscopic imperfections in the coating microstructure. They are most commonly formed by overgrowing of the topographical imperfections (pits, asperities) on the substrate surface or the foreign particles of different origins (dust, debris, flakes). Such foreign particles are not only those that remain on the substrate surface after wet cleaning procedure, but also the ones that are generated during ion etching and deposition processes. Although the origin of seed particles from external pretreatment of substrate is similar to all PVD coatings, the influence of ion etching and deposition techniques is rather different. Therefore, special emphasis is given on the description of the processes that take place during ion etching of substrates and the deposition of coating. The effect of growth defects on the functional properties of PVD coatings is described in the last section. How defects affect the quality of optical coatings, thin layers for semiconductor devices, as well as wear, corrosion, and oxidation resistant coatings is explained. The effect of growth defects on the permeation and wettability of the coatings is also shortly described.

Metallurgical Soldering of Duplex CrN Coating in Contact with Aluminum Alloy

Coatings deposited by physical vapor deposition (PVD) significantly reduce the wear of high pressure die casting tools; however, cast alloy soldering still has a strong negative effect on production efficiency. Although a lot of research has been already done in this field, the fundamental understanding of aluminum alloy soldering toward PVD coatings is still scarce. Therefore, in this work the performance of CrN duplex coatings with different roughness is evaluated by a modified ejection test performed with delayed (DS) and conventional casting solidification (CS). After the ejection tests, sample surfaces and layers were subjected to comprehensive characterizations of their morphological and chemical characteristics. Considerably lower values of the ejection force were recorded in DS experiments than in CS experiments. Surface roughness played an important role in the CS experiments, while samples with different surface topographies in the DS experiments performed in a similar fashion. The decrease in the ejection force, observed in DS tests, is attributed to the formation of a thick Cr–O layer on CrN coating which reduced soldering and sliding friction against thick Al–O casting scale. The Cr–O layer formed in DS experiments suffered from diffusion wear by cast alloy. The observed oxidation phenomena of nitride coatings may be utilized in a design of non-sticking coatings.

Nanotopographical Coatings Induce an Early Phenotype-Specific Response of Primary Material-Resident M1 and M2 Macrophages.

Implants elicit an immunological response after implantation that results in the worst case in a complete implant rejection. This biomaterial-induced inflammation is modulated by macrophages and can be influenced by nanotopographical surface structures such as titania nanotubes or fractal titanium nitride (TiN) surfaces. However, their specific impact on a distinct macrophage phenotype has not been identified. By using two different levels of nanostructures and smooth samples as controls, the influence of tubular TiO2 and fractal TiN nanostructures on primary human macrophages with M1 or M2-phenotype was investigated. Therefore, nanotopographical coatings were either, directly generated by physical vapor deposition (PVD) or by electrochemical anodization of titanium PVD coatings. The cellular response of macrophages was quantitatively assessed to demonstrate a difference in biocompatibility of nanotubes in respect to human M1 and M2-macrophages. Depending on the tube diameter of the nanotubular surfaces, low cell numbers and impaired cellular activity, was detected for M2-macrophages, whereas the impact of nanotubes on M1-polarized macrophages was negligible. Importantly, we could confirm this phenotypic response on the fractal TiN surfaces. The results indicate that the investigated topographies specifically impact the macrophage M2-subtype that modulates the formation of the fibrotic capsule and the long-term response to an implant.