Anti-wear Coatings Research Articles

Performance properties of electro-spark deposited carbide-ceramic coatings modified by laser beam

The work presented in this paper determines the influence of the laser treatment process on the properties of electrospark coatings. The properties after laser treatment were examined by microstructure analysis, microhardness, roughness and adhesion tests. The studies were conducted using WC–Co–Al2O3 electrodes produced by sintering nanostructural powders. The anti-wear coatings were first deposited by an EIL-8A apparatus on C45 carbon steel and then laser melted within various process parameters. In this case Nd:YAG laser (BLS 720 model) was applied. The electro-spark deposited coatings are very promising to improve abrasive wear resistance of tools and machine parts, which was indicated by tribological tests.

On the use of Fluidised Bed Coating (FBC) to deposit thin Al<SUB align=right>2O<SUB align=right>3 films onto metal substrates

Fluidised Bed Coating (FBC) is a viable and low-cost technique to apply, at ambient temperature, thin adherent ceramic coatings onto metal and non metal substrates. Al2O3 films, by virtue of its special thermo-mechanical, chemical, electrical and optical properties, belong to a class of ceramic coatings of particular interest in several manufacturing processes. In this respect, the present paper reviews selected applications in manufacturing of Al2O3 coated aluminium substrates. In particular, the use of fluidised bed deposited thin Al2O3 films has been reported as surface overlay coatings to improve the fatigue behaviour of aluminium components, as absorption and thermal barrier coatings in sheet laser forming and, finally, as anti-wear protective coatings.

Innovative anti-wear coatings on cutting tools for wood machining

The paper presents a study on the performances of innovative coatings for steel cutting tools in machining wood. A series of steel tools with different surface modifications, such as nitriding, application of antiwear DLC and CrN mono and multilayer coatings, has been applied to HSS18 and alloy steel 90CMV8 substrates. Tribological and erosion resistance of the samples was evaluated and related to the cutting performance, while surface analysis was carried out on the workmaterial at the end of the cutting tests. The overall tests indicated that the modified tools are promising in secondary transformation of wood. Furthermore, combined tribological and erosion studies allowed to individuate a wear mechanism and the possibility to foresee cutting performance in this application.

Cutting properties of the Al 2O 3 + SiC (w) based tool ceramic reinforced with the PVD and CVD wear resistant coatings

The paper presents investigation results of tribological properties of the coatings deposited with the PVD and CVD techniques on cutting inserts made from the Al 2O 3 + SiC (w) oxide tool ceramic. Tests were carried out on the multipoint inserts made from the Al 2O 3 + SiC (w) oxide ceramics, uncoated and coated with gradient, mono-, multilayer and multicomponent hard wear resistant coatings composed of TiN, TiCN, TiAlN, TiAlSiN and Al 2O 3 layers with PVD and CVD processes. Substrate hardness tests and microhardness tests of the deposited coatings were made on the ultra-micro-hardness tester. It was demonstrated, basing on the technological cutting tests of spheroidal cast iron, that putting down onto the tool ceramics the thin anti-wear coatings in the PVD and CVD processes increases their abrasion wear resistance, which has a direct effect on extending the tool edge life. Basing on the roughness parameter R a of the machined cast iron surface after the cutting tests, improvement was revealed of the machined material properties, cut with coated oxide ceramics compared to material machined with the uncoated tools.

Structure and properties of PVD and CVD coated Al 2O 3 + TiC mixed oxide tool ceramics for dry on high speed cutting processes

The paper presents investigation results of structure and properties of the coatings deposited with the PVD and CVD techniques on cutting inserts made from the Al 2O 3 + TiC oxide tool ceramic. The investigation includes the metallographic analysis on the transmission and scanning electron microscope, chemical composition analysis as well as the analysis of the mechanical and functional properties of the material. Tests were carried out on the multipoint inserts made from the Al 2O 3 + TiC oxide ceramics, uncoated and coated with multi-layer hard wear resistant coatings composed of TiN, TiCN, TiAlN, TiAlSiN and Al 2O 3 layers with PVD and CVD processes. It was demonstrated that adhered closely to each other were characterized by good adhesion to the substrate. It was demonstrated, basing on the technological cutting tests of grey cast iron, that putting down onto the tool ceramics the thin anti-wear coatings in the PVD and CVD processes increases their abrasion wear resistance, which has a direct effect on extending the tool edge life. Basing on the roughness parameter R a of the machined cast iron surface after the cutting tests, improvement was revealed of the machined material properties, cut with coated oxide ceramics compared to material machined with the uncoated tools.

Effect of depositing the hard surface coatings on properties of the selected cemented carbides and tool cermets

The paper presents results of the structural examinations, tests of mechanical and working properties of thin anti-wear coatings of the TiN/TiAlSiN/TiN type, deposited in the PVD process onto the substrate from the tool cermets and sintered carbides. Structural examinations are presented of the applied coatings and their substrate made on the scanning electron microscope and on the light microscope. Evaluation of the adhesion of the deposited coatings onto the sintered carbides and cermets was made using the scratch test. The lowest force L C called the critical load was determined based on the acoustic emission value (AE), at which loss of the coating adhesion to the substrate occurs. Cutting properties of the investigated materials were determined based on the technological continuous cutting tests of the C45E steel. Width of the wear band on the tool flank VB max = 0.2 mm was assumed as the cutting edge wear criterion for finishing. Substrate hardness tests and micro-hardness tests of the deposited coatings were made on the ultra-micro-hardness tester at 70 mN load. Surface roughness tests were also made before depositing the coatings and after completing the PVD process.

Investigation of antiwear coatings deposited by the pvd process

AbstractThe tribological properties of various PVD‐deposited coatings (vacuum arc method) have been tested, both single‐layer coatings (TiN, CrN, Ti(C,N), and Cr(C,N)) and multilayer coatings (Cr(C,N)/CrN/Cr and CR(C,N)/(CrN+Cr2N)/CrN/Cr). An unlubricated ball‐on‐disc tribosystem was used in which an Al2O3 ball is pressed against a coated steel disc rotating in the horizontal plane. A novelty of the method is the removal of wear debris from the contact zone using a draught of dry argon. This improves the repeatability of the test results and the stability of the tribological characteristics.It is shown that CrN coatings exhibit the best antiwear properties and Ti(C,N) the worst. Multilayer coatings have better antiwear properties than single‐layer ones. The friction coefficients for CrN and Cr(C,N) coatings are much smaller than for the commonly used TiN.A correlation has also been found between the physical properties of the coatings tested (adhesion of the coating to the substrate assessed in scratch tests, and coating hardness) and their antiwear properties. An improvement in coating‐substrate adhesion results in wear reduction, while greater hardness (causing a coating embrittlement increase and a change in the wear mechanism) brings about greater wear. There is no correlation between the physical properties and the friction coefficients of the coatings tested.

A method for the tribological testing of thin, hard coatings

AbstractA new method has been developed for tribological testing of thin, hard antiwear coatings, using a ball‐on‐disc tribosystem, under conditions of dry sliding. In this, an Al2O3 ball is pressed against a coated steel disc. Wear debris is removed from the contact zone by a stream of dry argon in this novel method. This improves the stability of the tribological properties and the repeatability of the test results. All test conditions are precisely defined, in particular: the type of motion, air relative humidity, ambient temperature, sliding speed, load, tribosystem spatial configuration, substrate material, substrate hardness and roughness, and coating thickness. The method developed has been used to test various physical vapour deposition coatings (deposited by the vacuum arc method), i. e., single‐layer TiN, Ti(C,N), CrN, and Cr(C,N), and multilayer Cr(C,N)/CrN/Cr and Cr(C,N)/(CrN+Cr2N)/CrN/Cr. It is shown that CrN coatings exhibit the best antiwear properties, and Ti(C,N) the worst. Friction coefficients for CrN and Cr(C,N) coatings are much lower than for the more commonly used TiN. Multilayer coatings have better antiwear properties than single‐layer ones.

Plasma physics and technology; industrial applications

Plasma technologies offer a wide spectrum of possible treatments of materials. In particular, in function of the peculiar physical characteristics of the plasma, produced by different ionisation systems, three types of processes on the materials can be activated: (1) Destruction of toxic/harmful materials; (2) Superficial modification of existing materials; (3) Creation of new materials. Thermal plasma can be used to destroy the solid, liquid and gaseous toxic halogenated and hazardous substances or to generate anticorrosion, thermal barriers, antiwear coatings, etc. Cold plasmas can be used for surface modifications of materials, ranging from the simple topographical changes to the creation of surface chemistries and coatings that are radically different with respect to the bulk material. Each of the three lines has a different weight with respect to an immediate industrial transferring. While the first two are ready for an immediate industrial utilisation of the processes, the third one is still under investigations. Some industrial processes will be described and, in the case of some treatments of toxic substances, a comparative cost analysis is presented.

206 Effect of hardness of mating materials on friction and wear of DLC films

DLC (diamond-like carbon) films are one of the best candidates as anti-wear coatings for high performance mechanical elements and electric devices that require tribological enhancement and chemical stability. Most of previous researches on DLC films were concerning with DLC film itself or its properties. However, tribological characteristics of DLC film should be affected by properties of mating materials. In this paper, four kinds of mating balls were prepared for tribological tests of DLC film. The mating balls were made with same material (stainless) but apply different annealing conditions. The effect of hardness of mating material on friction and wear of DLC films has been measured with precision friction tester. Testing results shows, the harder the mating materials, the lower the friction coefficient and wear rate among results of martensite balls. The reason of high friction coefficient in soft mating materials considers as widen the contact area during experiment. It can be proved by measuring wear profiles on DLC films and wear trace on mating balls.

An investigation of fretting behavior of ion-plated TiN, magnetron-sputtered MoS 2 and their composite coatings

All surface techniques can be roughly divided into two categories: anti-wear coatings characterized by high hardness and anti-frictions coatings with low friction coefficient. However, it is still unclear which kind of coatings is more effective for preventing the fretting damage so far. So it is of important meaning to conduct a comparative study on fretting-resistant behavior of these coatings. This paper analyzes the fretting properties and damage mechanism of ion-plated TiN, magnetron sputtered MoS 2 and their composite coatings on a SRV testing machine through a systematic examinations of wear scar and wear debris under SEM. The main results obtained in the slip regime showed that the fretting resistance of TiN coating was superior to that of MoS 2 coating, especially at high load and large number of cycles. Detachment of particles was the main reasons of degradation for both TiN and MoS 2 coatings, while the shape of the detached particles were quite different. The composite coating of TiN+MoS 2 showed excellent fretting-resistant performance under the same testing conditions, as the solid lubrication property of MoS 2 coating could be fully developed by a strong support from the underneath TiN coating, i.e., the advantages and disadvantages of two kinds of surface techniques could be mutually supplemented. In addition, the formation and effect of the third-body is discussed in detail as well.

Deposition of AlN layers by collimation magnetron sputtering

The aim of the work was to investigate the possibility of deposition of hard, antiwear coatings with high thickness homogeneity on inner surfaces of deep holes. A planar magnetron with a 100 mm diameter cathode and a “honeycomb”-type collimator was used. The influences of the collimator in the magnetron-substrate system and its geometrical parameters on the current-voltage characteristics of the discharge were checked. Using a Langmuir probe, the ionic current which flows through the collimator was measured. The chemical composition, morphology and thickness distribution of deposited materials were investigated. Investigations of the optical density and reflectance of layers deposited with and without the use of a collimator let us check the change of their optical properties.

Mechanical and optical properties of ITO films with anti-reflective and anti-wear coatings

In this study, radio frequency (rf) magnetron sputtered ITO films were coated with reactively sputtered SiO 2 films. The microhardness, pull-off strength, scratch adhesion strength, optical transmittance and reflectance of the SiO 2/ITO/substrate system are investigated. Coating of SiO 2 enhances both the hardness and pull-off strength and reduces the scratch critical load of the system. The optical transmittance in the visible range is also improved with the addition of SiO 2.

Characterization of wear protective coatings

Arising from the necessity and the suitableness of wear protection by coatings, common coating techniques and treatment procedures are presented in a survey. For evaluation of the effectiveness of these anti-wear coatings a testing process was proposed consisting of three parts: (1) a test procedure to simulate the basic wear mechanisms; (2) investigations of the tribologically relevant material properties; (3) an integral wear test procedure. Taking thermal sprayed coatings and electrolytic depositions as examples, the characterization procedure is explained. The test systems designed at the Technical University Chemnitz-Zwickau for simulation of the basic mechanisms of adhesive and abrasive wear and long-term fatigue-wear are described with regard to the functional principle, the structure and the parameters to be ascertained.

An XPS Study of the Chemical Interactions of the Extreme Pressure Lubricant Additive Lead Naphthenate with Titanium and Titanium Compound Surfaces

The surface chemical interactions between boundary or extreme pressure (EP) lubricant additives and the mechanical components they protect often determine the performance and life of marginally lubricated and highly loaded mechanisms. Most of these additives have been developed for use with steel components, and a lack of fundamental understanding regarding the surface bonding and reactivity occurring in the mechanical contact severely limits the application of these additives to mechanisms incorporating new materials. This work examines the chemical interactions between the EP additive lead naphthenate (Pbnp) and a series of titanium-based materials (Ti, TiB{sub 2}, TiC, TiN, and TiO{sub 2}). These X-ray photoelectron spectroscopy (XPS) studies show that Pbnp applied via solution chemisorbs to all of these materials and that the surface activity is enhanced by damaging the substrate (i.e., wear) during exposure. In addition, both Ti and TiB{sub 2} are capable of chemically reducing Pbnp to metallic lead, while TiO{sub 2} stabilizes and oxidized form of lead. Neither TiC nor TiN, the most widely used of these materials for antiwear coatings, is capable of chemically reducing Pbnp or of retaining significant amounts of Pbnp fragments at elevated temperature. The results indicate that Pbnp is probably not a good candidate asmore » an EP additive for TiC and TiN coatings. 33 refs., 17 figs., 4 tabs.« less

Friction and wear of uncoated or SiO 2-coated 329 stainless steel and of uncoated or AlN-coated aluminium surfaces

We have investigated the surface wear resistance of disks made of uncoated or SiO 2-coated 329 stainless steel and of uncoated or AlN-coated commercial aluminium. The stainless steel disks were given three types of surface finish (ground, lapped and polished) and all samples were subsequently given antiwear coatings (silica on stainless steel and aluminium nitride on aluminium) by ion-beam-assisted deposition in order to try to improve their resistance to wear. Testing was carried out in a fully automated pin-on-disk system. The results show considerably increased wear resistance for coated samples. Some properties relating to the finish of uncoated samples were also noted.

Abrasion, erosion and scuffing resistance of carbide and oxide ceramic thermal sprayed coatings for different applications

In the area of antiwear coatings, carbide-containing coatings ( Cr 3 Cr 2-NiCr, WC-Co, WC-Ni etc.) and oxide ceramic coatings ( Al 2 O 3, Cr 2 O 3 etc.) are applied using different thermal spray processes in the form of individual layers. In many industries these coatings have become technically significant on components where wear and friction can cause critical damage in the form of abrasion, erosion and scuffing together with corrosion. Carbide-containing and ceramic coatings have been produced with different thermal spray processes (atmospheric plasma spraying, vacuum plasma spraying, high velocity flame spraying and detonation gun spraying) for the determination of abrasive, adhesive and erosive wear resistance. Two types of abrasion test, namely an adhesion wear test and an erosion test in water at a high velocity (up to 170 m s −1), were used for the characterization of wear resistance under different conditions. The coatings were also characterized with regard to microstructure, composition and fracture toughness. The influence of the thermal spraying process parameters on the microstructure is presented together with the influence of the microstructure on the behavior of the coatings under simulated service conditions.

Multitechnique problem solving using EDS/EPMA and surface analysis

Thin films are used in a wide range of modern technologies. Examples include sensors, antiwear coatings, optical coatings, and integrated circuits. A variety of methods have evolved for characterizing thin films in the thickness range of 1 monolayer to several micrometers. Electron probe microanalysis (EPMA) or energy dispersive x-ray spectroscopy (EDS) are two methods for characterizing thicker films (>1 μm). In these techniques, the sampling depth depends on the penetration depth of the primary electron beam which can be controlled by changing the electron beam energy. Thin films can also be characterized using line scans on specimens prepared as polished cross-sections or after angle lapping. For extremely thin films (<3 nm), techniques with high surface sensitivity such as Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) are commonly employed. Sampling depth depends on the attenuation length of the emitted photoelectrons or Auger electrons.Electron spectroscopy techniques are also used to characterize thicker films by adding a microsectioning method to the experiment, most commonly ion sputtering.

An investigation of antiwear coatings on fibre-reinforced plastics

Some mechanical applications of fibre-reinforced plastics are presently presented by their poor surface properties, like hardness, wear and thermal resistance. This paper deals with the possibility of improving all these properties by a coating of metallic or ceramic nature, having certain basic requirements for the possible applications. Analysis on coats carried out by means of different types of processes on glass and carbon fibre-reinforced epoxy is performed by mechanical and tribological tests and metallographic analysis and the results are compared to each other and with a traditional coat on steel as well.

Reactive d.c. high-rate sputtering as production technology

We discuss process parameters that influence the deposition of layers with dedicated stoichiometry in terms of the fundamentals of reactive d.c. sputter processes with magnetron sources. We introduce the term “basic stability” of reactive sputter arrangements and describe their variants. To make the industrial production of films from chemical compounds profitable, however, it is necessary to work in the unstable transition mode. We discuss methods for process stabilization and present new approaches by using a plasma-emission monitor (PEM) and a self-stabilizing arrangement for the long-term deposition of insulating films. When working with the PEM control loop, the reactive d.c. sputter process can be stabilized even at close coupling between target and substrate. To exemplify various production techniques with different requirements, we compare indium-tin oxide (ITO), Cr-Si-O and TiN layers. The PEM control allows the deposition of ITO layers at a defined degree of oxidation to obtain minimum resistivities of ϱ < 4.5 × 10-4 Ω cm at a high transparency. The self-stabilizing coating technique yields homogeneous, very thick, hard Cr-Si-O antiwear coatings at rates much higher than those of metal sputtering. For optimized TiN layers on tools, the plasma density is of decisive importance in attaining a fine-grained structure. A large increase in the power density on the target and the use of a bias for film deposition under ion action yield film properties of outstanding quality.