Wear Protection Applications Research Articles

A 3D printing route to fabrication of ZrCuSi alloy target for ZrCuSiN nanocomposite thin films

The present study demonstrates a simple and robust strategy for fabricating nanocomposite thin films with high quality using a multi-component ZrCuSi single target. The ZrCuSi target was produced by using computer numerical control (CNC) based direct energy deposition (i.e., 3D printing). The influence of the energy density on morphological features and porosity of the ZrCuSi target surface was closely examined at a certain range of the energy density (75–225 J/mm3). X-ray diffractometer (XRD) and scanning electron microscopy (SEM) were applied for confirming the presence of the preferable crystallographic orientation and elucidating the morphological features of the nanocomposite target. In addition, functional nanocomposite thin films deposited from the ZrCuSi target presented in the current study were characterized. A scratch test and field-emission SEM (FE-SEM) revealed the adhesion properties and the morphological features of the nanocomposite coatings. Therefore, this work is highly expected to provide a facile and robust way to fabrication of e multi-component functional targets based ZrN, thereby envisioning usefulness of the nanocomposite coatings for automotive engine parts and various other wear protection applications.

Microstructure and Mechanical Properties of ZrCuSiN Coatings Deposited by a Single Alloy Target

Recently, research has been conducted on nanocomposite thin films containing new additive elements in ZrN. In this paper, a method for depositing ZrCuSiN nanocomposite coatings using a ZrCuSi single target is presented. The ZrCuSi target that was used to easily deposit a ZrCuSiN coating in a mixed gas atmosphere (Ar + N2) was produced by a simple arc melting method (casting process). The effect of the nitrogen content was investigated by depositing a ZrCuSiN coating using alloy targets at various nitrogen gas flow rates (2, 4, 6, and 8 sccm). X-ray diffraction analysis of the ZrCuSiN coatings revealed a ZrN structure with a preferable orientation (200). As the nitrogen flow rate increased, the formation of o-Zr3N4 was dominant in the ZrN formation. A nitrogen gas flow rate of 4 sccm produced a coating with optimal ZrN and a-Si3N4 coordination and maximum hardness (41 GPa). Reciprocal friction tests of all coatings and uncoated carburized SCM415 steel in a 5W30 lubrication atmosphere demonstrated that the 4 sccm coating had the lowest friction coefficient (0.002). Therefore, our method has the potential to be an alternative surface coating technique for materials used in automotive engine parts and various other wear protection applications.

Evaluation of the Adhesion and Slurry Wear Erosion of Nb2O5 Coatings Applied by Flame Spray

Niobium pentoxide (Nb2O5) has excellent chemical and thermodynamic stabilities, characteristics that have accelerated the applications of this material in the form of coatings to protect against corrosive processes. However, few studies have evaluated its performance in wear protection applications. In this research, the slurry wear erosion resistance of Nb2O5 coatings deposited by flame spray was studied. The microstructural characterization of the coatings was performed by optical microscopy and scanning electron microscopy (SEM) assisted by chemical analysis by energy dispersive X-ray spectroscopy (EDS). Adhesion of the coatings was determined by the adhesion test (ASTM C633-13). Image analysis was used for the quantitative study of the adhesion tested areas and porosity of the coatings. Erosive wear resistance was determined using a container tribometer with erosive mixing at a particle velocity of 9.33 m/s and two particle incidence angles. The thinner coatings had fewer microstructural defects, such as pores and microcracks, and greater adhesive strength. The thicker coatings presented a cohesive failure mode. When the impact angle of the erodent particles was 90 deg, the thickness of the Nb2O5 coatings should not exceed 350 μm. Nb2O5 coatings applied by flame spray showed good resistance to slurry wear erosion, besides inherent low cost and flexibility of the process.

CVD Coating of Oxide Particles for the Production of Novel Particle-Reinforced Iron-Based Metal Matrix Composites

This paper focuses on surface metallization of oxide particles by means of titanium nitride (TiN) thin films for the production of highly wear-resistant metal matrix composites (MMC) on Fe-base for wear protection applications. These powder-metallurgically produced materials consist of a metallic matrix with embedded oxide hard-particles such as alumina or zirconia. The poor wettability of these oxides by iron-base melts and the resulting weak bonding between the components lead to porous materials and weak tribomechanical properties, thus limiting the material’s application range. To counteract such problems, this paper describes a processing route in which the oxide particles are pre-metallized by application of a thin TiN coating by means of chemical vapor deposition (CVD). This surface metallization should increase the wettability and bonding behavior between the ionically bonded particles and the iron-base alloy, which should improve the mechanical and tribological properties. Therefore, a CVD device for coating ceramic particles was constructed and is described in this paper. Furthermore, coatings deposited on the ceramic sub-strates were investigated by means of RBS, SEM and XRD. In addition, the feasibility of producing metal matrix composites (MMC) by admixing the TiN-coated oxide particles with a Fe-base alloy and their further densification by supersolidus liquid-phase sintering is demonstrated.

Application of hardmetals as thermal spray coatings

Thermally sprayed hardmetal coatings have a typical thickness within the range 100–500μm. Thus, thermal spray enables the functionality of hardmetals to be realized on the surface of large parts, which cannot be produced by powder metallurgy for technical and economical reasons. This article reviews the different types of thermal spray processes, with particular focus on the high velocity HVOF and HVAF deposition techniques which are of most relevance to the application of hardmetal coatings. Feedstock powder preparation technologies are presented. The majority of hardmetal thermal spray coatings are based either on WC or Cr3C2 or hard phases appearing as a result of their interaction. As an alternative, TiC-based compositions are most intensively studied. Thermal spraying generates significant changes in the hardmetal chemical and phase compositions between the feedstock powder to the sprayed coating. Coating formation and microstructures as well as selected properties, such as hardness, the effect of heat treatments and the oxidation in service, as well as corrosion resistance are discussed. As an example for wear protection applications, abrasion wear resistance is shortly discussed.This paper is a partly updated and condensed version of the chapter: “Coatings by thermal spray” in the book “Comprehensive Hard Materials”, V.K. Sarin (Editor-in-Chief) & D. Mari & L. Llanes (Vol. Ed.), Vol. 1 (pp. 471–506), Elsevier, 2014.

Supersolidus liquid-phase sintering of ultrahigh-boron high-carbon steels for wear-protection applications

Abstract Powder metallurgy (PM) represents an alternative to conventional casting processes for the production of wear-resistant materials. PM hard alloys for wear-protection applications feature both higher strength and fracture toughness compared to cast hard alloys due to their more finely grained microstructure. However, densification by hot-isostatic pressing (HIP), the conventional PM-compaction method, is relatively expensive and thus partially counteracts low-cost processing. To increase the economic efficiency of the processing route, supersolidus liquid-phase sintering (SLPS) was investigated. In addition, expensive Ni- and Co-base hard alloys were substituted by boron-rich Fe-base hard-facing alloys. In this study, three ultrahigh-boron hard-facing alloy powders were densified by SLPS and HIP. The sintering temperatures were optimized by means of sintering experiments that were supported by thermodynamic calculations. Both densification states were investigated and compared with respect to the microstructure and the tribological and mechanical properties of the compacted hard-facing alloys. It was shown that the mechanical and tribological properties are strongly influenced by the microstructure. Although the microstructure is affected by the chemical composition, it can also be adapted by the densification process. SLPS-densified hard-facing alloys have a coarse microstructure that imparts not only a high wear resistance but also a detrimental effect on the mechanical properties.

High Velocity Oxy Fuel Spraying of Cold Work Tool Steels‐ A Novel Approach to Thick Coatings for Wear Protection Applications

AbstractWithin this work, HVOF sprayed coatings based on X220CrVMo13‐4 cold work steel were applied to a S235JR construction steel substrate. The investigations focus on the influence of particle size and spray parameters on the coating microstructure, analyzed by means of optical microscope (OM) and scanning electron microscopy (SEM). Additional XRD measurements and micro hardness plots across the interface between substrate material and coating were carried out. Furthermore, the influence of particle size on the detected phases and coating porosity was studied. The results were compared with an X220CrMoV13‐4 reference sample produced by HIP.

Investigation of Properties and Wear Behavior of HVOF Sprayed TiC-Strengthened Fe Coatings

High-velocity oxyfuel (HVOF) sprayed carbide based coatings (such as Cr3C2/NiCr) are industrially well established for wear protection applications. Due to their high carbide content of typically 75 wt.% and more, they provide very high hardness and excellent wear resistance. Unfortunately, costs for matrix materials such as nickel underlie strong fluctuations and are normally well above the prices for iron. Therefore an alternative concept to conventional carbides is based on TiC-strengthened low-cost Fe-base materials, which are already used for sintering processes. Depending on the carbon content, the Fe-base material can additionally offer a temperable matrix for enhanced wear behavior. The sprayability of TiC-strengthened Fe-powders with a gaseous and a liquid fuel driven HVOF system was investigated in this study. The resulting coatings were analyzed with respect to microstructure, hardness, and phase composition and compared with galvanic hard chrome, NiCrBSi, and Cr3C2/NiCr (80/20) coatings as well as with sintered Fe/TiC reference materials. Furthermore, the Fe/TiC coatings were heat treated to proof the retained temperability of the Fe matrix after thermal spray process. Tribometer tests (pin-on-disk tests) were conducted to determine wear properties.

Investigation about the Chrome Steel Wire Arc Spray Process and the Resulting Coating Properties

Nowadays, wire-arc spraying of chromium steel has gained an important market share for corrosion and wear protection applications. However, detailed studies are the basis for further process optimization. In order to optimize the process parameters and to evaluate the effects of the spray parameters DoE-based experiments had been carried out with high-speed camera shoots. In this article, the effects of spray current, voltage, and atomizing gas pressure on the particle jet properties, mean particle velocity and mean particle temperature and plume width on X46Cr13 wire are presented using an online process monitoring device. Moreover, the properties of the coatings concerning the morphology, composition and phase formation were subject of the investigations using SEM, EDX, and XRD-analysis. These deep investigations allow a defined verification of the influence of process parameters on spray plume and coating properties and are the basis for further process optimization.

Growth structure and growth defects in pulsed laser deposited Cr–CrN x–CrC xN 1− x multilayer coatings

Chromium carbonitride (CrC x N 1− x ) coatings are becoming more and more interesting for wear protection applications due to their increased hardness and improved wear performance compared to chromium nitride (CrN x ) hard coatings. Further improvements seem to be possible by using multilayer coatings of these two materials. In the current work such multilayer structures were deposited by the Pulsed Laser Deposition (PLD) technique at room temperature using an industrially designed 4-beam multi-spot PLD evaporator. The coatings were investigated by means of transmission electron microscopy (TEM) in order to solve their growth mechanisms and microstructure development. Due to the very high hardness and brittleness of the coatings, the TEM sample preparation has to be based on gallium focused ion beam cutting. Although the chemical analyses revealed a significant Ga atom contamination of the samples originating from the sample preparation, the face-centered cubic CrN-based phases and their textures, found in electron micro-diffraction analyses as well as in X-ray diffraction measurements, were scarcely influenced by the incorporated atoms. Great influences on the phase formation result from oxygen atom trapping from the rest gas atmosphere prior deposition. A very fine grained (2–5 nm) structure was found for the pure chromium adhesive interface layers, which are necessary for high adhesion of the hard coating layers. These hard ceramic layers–CrN x and CrC x N 1− x –possess much coarser (8–15-nm grain size), micro-columnar structures. Furthermore, influences on the film growth are caused by defects on the substrate surface like cracks and contaminating dust particles.

Pulsed laser deposition of titanium oxide coatings at room temperature?structural, mechanical and tribological properties

Titanium oxide (TiO x ) coatings exhibit extraordinary optical, electrical and tribological properties, but very less is known about coatings deposited at room temperature. In the present work this gap was closed by employing the room temperature pulsed laser deposition (PLD) technique. In order to simulate different deposition conditions, the substrate (AISI M2, molybdenum) surfaces were situated parallel (‘on-axis’ geometry) and perpendicular (‘off-axis’) to the pure titanium targets ablated by the Nd:YAG lasers with a wavelength of 1064 nm. The combination of a four-beam PLD evaporator with a suitable movement of the substrates resulted in a high-rate film growth on large surfaces. The coating structure investigated by X-ray diffraction consists of a mixture of monoclinic β-TiO 2 and amorphous TiO x phase. The ratio of the amount of the phases, the hardness and the elastic constants strongly depend on the O 2 gas pressure and the target–substrate arrangement applied for deposition. Owing to the very high adhesion and their very smooth surfaces, the TiO x coatings exhibit friction coefficients of approximately 0.55 and wear rates of lower than 10 −15 m 3 N −1 m −1 , turning out that titanium oxide coatings deposited by means of PLD are very promising candidates for wear protection applications.

Pulsed laser deposition of titanium oxide coatings at room temperature—structural, mechanical and tribological properties

Titanium oxide (TiO x ) coatings exhibit extraordinary optical, electrical and tribological properties, but very less is known about coatings deposited at room temperature. In the present work this gap was closed by employing the room temperature pulsed laser deposition (PLD) technique. In order to simulate different deposition conditions, the substrate (AISI M2, molybdenum) surfaces were situated parallel (‘on-axis’ geometry) and perpendicular (‘off-axis’) to the pure titanium targets ablated by the Nd:YAG lasers with a wavelength of 1064 nm. The combination of a four-beam PLD evaporator with a suitable movement of the substrates resulted in a high-rate film growth on large surfaces. The coating structure investigated by X-ray diffraction consists of a mixture of monoclinic β-TiO 2 and amorphous TiO x phase. The ratio of the amount of the phases, the hardness and the elastic constants strongly depend on the O 2 gas pressure and the target–substrate arrangement applied for deposition. Owing to the very high adhesion and their very smooth surfaces, the TiO x coatings exhibit friction coefficients of approximately 0.55 and wear rates of lower than 10 −15 m 3 N −1 m −1, turning out that titanium oxide coatings deposited by means of PLD are very promising candidates for wear protection applications.

Interactions between tungsten carbide (WC) particulates and metal matrix in WC-reinforced composites

A variety of experimental techniques have been used to investigate the interactions between tungsten carbide (WC–Co 88/12) particulates and the matrix in some new wear resistant cobalt-based superalloy and steel matrix composites produced by hot isostatic pressing. The results show that the chemical composition of the matrix has a strong influence on the interface reaction between WC and matrix and the structural stability of the WC particulates in the composite. Some characteristics of the interaction between matrix and reinforcement are explained by the calculation of diffusion kinetics. The three-body abrasion wear resistance of the composites has been examined based on the ASTM G65-91 standard procedure. The wear behavior of the best composites of this study shows great potential for wear protection applications.

Synthesis of Si–C–N coatings by thermal Plasmajet chemical vapour deposition applying liquid precursors

AbstractMaterials in the system Si–C–N feature excellent properties for wear protection applications, even at elevated temperatures, and an excellent thermal shock resistance. As these materials have no melting point, coatings have to be manufactured via a synthesis. Conventional chemical vapour deposition (CVD) processes have the disadvantage of low deposition rates. Thermal Plasmajet CVD processes with liquid feedstock feature the highest deposition rates among the gas‐phase synthesis processes. Single and triple DC torches and HF torches with supersonic nozzles have successfully been applied to produce Si–C(–N) coatings on different steel, aluminium, titanium and copper alloys, as well as on graphite. Besides chlorosilanes, hexamethyldisiloxane, tetramethyldisiloxane and hexamethyldisilazane have been used as liquid single precursors. Deposition rates up to 1500 μm h−1 have been achieved. The coatings show cauliflower, columnar or dense morphology and an amorphous or nanocrystalline structure. The formation of both α‐ and β‐Si3N4 has been verified by X‐ray diffraction. The application of chlorosilanes always results in chlorine‐containing coatings. The chlorine causes severe corrosion in the interface to mild carbon steel substrates. The processes are compared taking into account their characteristics concerning the injection modes, gas temperature and velocity profiles determined by enthalpy probe measurements. The process conditions are correlated to the coating microstructure and the adhesion to the substrates and guidelines for the optimum production of ­Si–C–N coatings by Plasmajet CVD are deduced. Emission spectroscopy is used to determine the mechanisms of the coating formation. Full dissociation of the liquid feedstock in the plasma jet has been verified. Copyright © 2001 John Wiley & Sons, Ltd.

Non-destructive characterization of mechanical and structural properties of amorphous diamond-like carbon films

Amorphous diamond-like carbon (DLC) films show promising properties for wear protection applications. Pulsed laser deposition (PLD), laser-induced pulsed vacuum arc deposition (laser-arc) and mass-selected ion beam deposition (MSIBD) are techniques which enable deposition of DLC films with the desired properties by providing sufficiently high carbon energy. Two non-destructive methods were used to determine the properties of films deposited by these three deposition techniques: (1) ellipsometry, which gives information about the micro-structure through the optical properties; and (2) laser-acoustic analysis enabling the measurement of the Young's modulus of thin films down to less than 100 nm film thickness. These methods were used to investigate the effect of the carbon ion energy and the substrate temperature during deposition on the film quality. A clear correlation between the Young's modulus and the optical parameters was found. All three deposition techniques are characterized by a critical substrate temperature above which sp 2 rich films are deposited. The PLD and MSIBD systems have a higher ion energy and a lower deposition rate than the laser-arc system. This is the reason for the higher critical substrate temperature below which sp 3 rich films are formed for PLD and MSIBD compared with laser-arc.

Improvement in low temperature ductility of molybdenum by a small addition of nickel

Powder metallurgy (PM) represents an alternative to conventional casting processes for the production of wear-resistant materials. PM hard alloys for wear-protection applications feature both higher strength and fracture toughness compared to cast hard alloys due to their more finely grained microstructure. However, densification by hot-isostatic pressing (HIP), the conventional PM-compaction method, is relatively expensive and thus partially counteracts low-cost processing. To increase the economic efficiency of the processing route, supersolidus liquid-phase sintering (SLPS) was investigated. In addition, expensive Ni- and Co-base hard alloys were substituted by boron-rich Fe-base hard-facing alloys.In this study, three ultrahigh-boron hard-facing alloy powders were densified by SLPS and HIP. The sintering temperatures were optimized by means of sintering experiments that were supported by thermodynamic calculations. Both densification states were investigated and compared with respect to the microstructure and the tribological and mechanical properties of the compacted hard-facing alloys. It was shown that the mechanical and tribological properties are strongly influenced by the microstructure. Although the microstructure is affected by the chemical composition, it can also be adapted by the densification process. SLPS-densified hard-facing alloys have a coarse microstructure that imparts not only a high wear resistance but also a detrimental effect on the mechanical properties.

Characterization of thermally sprayed coatings for high temperature wear protection applications

Under normal high temperature gas-cooled reactor (HTGR) operating conditions, faying surfaces of metallic components under high contact pressure are prone to friction, wear and self-welding damage. Component design calls for coatings for the protection of the mating surfaces. Anticipated operating temperatures of up to 850–950 °C (1562–1742 °F) and a design life of 40 years require coatings with excellent thermal stability and adequate wear and spallation resistance. In addition, they must be compatible with the HTGR coolant helium environment. Plasma- and detonation-gun-deposited chromium-carbide-base and stabilized zirconia coatings are under consideration for wear protection of reactor components such as the thermal barrier, heat exchangers, control rods and turbomachinery. Programs are under way to investigate the structural integrity, helium compatibility and tribological behavior of relevant sprayed coatings. In this paper the need for the protection of critical metallic components and the criteria for the selection of coatings are discussed. The technical background to coating development and the experience with the steam cycle HTGR are commented on. Coating characterization techniques employed at the General Atomic Company are presented, and the progress of the experimental programs is briefly reviewed. In characterizing the coatings for HTGR applications, it is concluded that a systems approach to establish correlation between coating process parameters and coating microstructural and tribological properties for design consideration is required.