Metal Matrix Composite Coatings Research Articles

Nanocrystalline Y2O3-modified metal matrix composite coatings with improved resistance to thermocyclic oxidation and V2O5-induced type II hot corrosion

Incorporating reactive elements (RE) into turbine coatings is a well-established surface treatment. However, suboptimal RE concentrations can lead to compromised strength, heightened brittleness, and reduced adhesion. In contrast, RE oxides offer advantages of avoiding these detrimental effects, counteracting corrosion phenomena induced by V2O5 compounds and enhancing oxidation resistance. A notable challenge lies in optimizing RE oxide particle incorporation and understanding the influence of particles in coating microstructures. This study focuses on developing NiAl and Ni-Cr-Al type metal matrix composite (MMC) coatings on Inconel 617 (IN617), containing up to 11 vol% of Yttria (Y2O3) nanoparticles. Y2O3 nanoparticles and Ni were co-electrodeposited on IN617 followed by either pack aluminizing or a two-step chromizing and aluminizing process. An even distribution of Y2O3 nanoparticles was observed throughout the entire 100 μm coating thickness, leading to significant grain refinement in the sub-micron to nano range in both coating types. Y2O3-strengthened coatings were subjected to oxidation at 1100 °C and hot corrosion at 700 °C and were compared to their Y2O3-free counterparts. Present at grain boundaries, Y2O3 markedly enhanced the oxidation and corrosion resistance by reducing interdiffusion, improving the oxide scale adherence and binding V2O5, highlighting the potential of this method for advanced turbine blade coatings.

Developing rotary swaging process for improving the performance of wire-arc sprayed Al/Al2O3 composite coating

Wire-arc sprayed Al-based composite coatings attracted great attentions due to their prospective application in offshore engineering. However, the difficulty in regulating ceramic reinforcements limited the performance of these coatings. In this work, we proposed a novel rotary swaging (RS) process to improve the deposition of ceramic particles, thus the Al/Al2O3 composite coating was prepared and evaluated in comparison with the traditional coating by spraying the drawing cored wires. As expected, the RS process promotes the melt of Al2O3 particles, leading to a significant increase of their deposition fraction with the simultaneous improvement in coating compactness and the interfacial bonding of heterogeneous splats. The sufficient melt of Al2O3 particles is attributed to the enhanced cohesion strength of filled powders to bear the vibration of arc force and facilitate heat transport. The explored composite coating displays a superior corrosion resistance in 3.5 wt% NaCl aqueous solution, due to the reduced active area on electrode surface and the lower sensitivity to pitting. Benefiting from a dynamic self-reinforcing effect, the explored composite coating presents lower coefficient of friction and significantly enhanced wear resistance under dry frictional condition. The present results demonstrate a great potential of the developed Al/Al2O3 composite coating in offshore application and provide an inspiration for future works aiming to exploit the high-performance metal-matrix composite coatings synthesized by low-cost wire-arc spraying.

Deposition characteristics and tribological performance of atmospheric plasma sprayed diamond metal matrix composite (DMMC) coatings

Diamond-reinforced metal matrix composites (DMMC) have great potential for wear-resistance applications due to the superior hardness imparted by diamond. Atmospheric plasma spraying involving axial injection of suitable feedstock is a convenient pathway to fabricate DMMC coatings for tribological applications. In this paper, thick DMMC coatings were deposited by plasma spraying Ni–P clad diamond particles under varying spray conditions. It was found that the phase characteristics of DMMC coatings as well as extent of diamond retention and fragmentation were significantly influenced by spray conditions such as, stand-off distance (SOD) and carrier gas flow rate (CGFR). Mechanical characterization (by micro-indentation) on all DMMC coatings developed in this work showed that coatings sprayed with longer SOD and higher CGFR has relatively higher hardness than other two coatings. However, on nanoindentation, the diamond hardness was found overestimated due to effect of diamond roughness on fragmentation. Ball-on-disc wear testing showed excellent tribological properties in all cases, with enhanced wear performance being noted when more diamond is retained in the coating.

Wear-resistant nickel-matrix composite coatings incorporating hard chromium carbide particles

This work evaluates the influence of plating variables on the morphology, composition homogeneity, and abrasive wear resistance of metal matrix composite coatings. A set of Ni/Cr3C2 coatings were brush plated onto steel coupons modifying two key variables: particle size and brush material. Compositional maps of unprecedented detail have been produced and analysed statistically to enhance understanding of composition distribution. The use of Abbott-Firestone curves to analyse surface morphology enabled the evaluation of valley and peak features. The coating differences highlighted by previous analyses have been compared with their behaviour in abrasive environments, simulated using Taber testing. Moreover, coupling Taber testing with partial compositional maps at different wear stages enabled monitoring of coating wear evolution. This methodology has revealed the importance of particle sedimentation during plating, which increased particle incorporation in the composite coating but also increased composition heterogeneity. The smaller 1.7 μm carbides and abrasive brushes produced coatings with more homogeneous morphologies, higher particle content, and increased resistance against abrasive wear, with a 60% reduction in material loss in comparison to the standard nickel coatings.

High-temperature tribological performance of functionally graded Stellite 6/WC metal matrix composite coatings manufactured by laser-directed energy deposition

Wear-driven tool failure is one of the main hurdles in the industry. This issue can be addressed through surface coating with ceramic-reinforced metal matrix composites. However, the maximum ceramic content is limited by cracking. In this work, the tribological behaviour of the functionally graded WC-ceramic-particle-reinforced Stellite 6 coatings is studied. To that end, the wear resistance at room temperature and 400 °C is investigated. Moreover, the tribological analysis is supported by crack sensitivity and hardness evaluation, which is of utmost importance in the processing of composite materials with ceramic-particle-reinforcement. Results indicate that functionally graded materials can be employed to increase the maximum admissible WC content, hence improving the tribological behaviour, most notably at high temperatures. Additionally, a shift from abrasive to oxidative wear is observed in high-temperature wear testing.

US patent expands Hardide's IP portfolio

Hardide Plc, a UK company that develops, manufactures and sells tungsten carbide and tungsten metal matrix composite coatings, has secured a patent from the US Patent Office that covers its water droplet erosion resistant coatings for turbine blades and other components.

Perspectives on Developing Burn Resistant Titanium Based Coatings-An Opportunity for Cold Spraying.

Titanium alloys are crucial lightweight materials; however, they are susceptible to spontaneous combustion under high-temperature and high-pressure conditions, limiting their widespread use in aerospace engines. Improving the burn resistance of Ti alloys is essential for the structural safety and lightweight of aerospace equipment. Burn-resistant Ti alloys, such as Ti-V-Cr and Ti-Cu, however, face limitations such as high cost and low specific strength. Surface coatings provide a cost-effective solution while maintaining the high specific strength and good processability of the base material. Conventional surface treatments, such as laser cladding, result in defects and deformation of thin-walled parts. Cold spray technology offers a promising solution, as it uses kinetic energy to deposit coatings at low temperatures, avoiding defects and deformation. In this paper, we review the current research on burn-resistant surface technologies of Ti alloys and propose a new method of bimetallic coating by cold spraying and low-temperature heat treatment, which has the potential to solve the problem of spontaneous combustion of aerospace engine parts. The strategy presented can also guide the development of high-performance intermetallic compound-strengthened metal matrix composite coatings.

An effective approach to improve microstructure and tribological properties of cold sprayed Al alloys

Abstract Cold spray is considered as an emerging technique for preparing wear-resistant metal matrix composite coatings on the surface of various kinds of metallic materials. In this work, a viable strategy of “cold spraying + hot rolling post-treatment” was successfully applied to prepare wear-resistant B4C/6061 Al composite coating on commercially available 6061 Al plates. The results revealed that hot rolling post-treatment results in uniform distribution of B4C particles in the alloy matrix, good inter-splat bonding, and sufficient plasticity in the splats through effective healing of the defects and splat boundaries in the as-sprayed deposit. As a result, the coating/substrate bonding strength in the hot rolled sample increased two-fold when compared with that of the as-sprayed sample. Moreover, hot rolling process resulted in much improved tribological properties of the coating with the wear rate ∼40% of that of the substrate. The obtained results indicated that the idea of combining cold spraying and hot rolling treatment is quite effective for improving the tribological properties of Al alloy plates. Further, this approach seems equally good for repairing/remanufacturing of unserviceable 6061 Al alloy components.

Residual stresses in Cu matrix composite surface deposits after laser melt injection

AbstractTungsten carbide particles reinforced metal matrix composite (MMC) coatings can significantly improve surface wear resistance owing to their increased surface hardness. However, the presence of macro‐ and micro‐residual stresses in MMC coatings can have detrimental effects, such as reducing service life. In this study, neutron diffraction was used to determine the residual stresses in spherical fused tungsten carbide (sFTC) reinforced Cu matrix composite surface deposits after laser melt injection. We also developed a thermo‐mechanical coupled finite element model to predict residual stresses. Our findings reveal that sFTC/Cu composite deposits produced with a preheating temperature of 400°C have low residual stresses, with a maximum tensile residual stress of 98 MPa in the Cu matrix on the top surface. In contrast, the sFTC/bronze (CuAl10Ni5Fe4) composite deposit exhibits very high residual stresses, with a maximum tensile residual stress in the Cu matrix on the top surface reaching 651 MPa. These results provide a better understanding of the magnitudes and distributions of residual stresses in sFTC‐reinforced Cu matrix composite surface deposits manufactured via laser melt injection.

Localised surface modification of high-strength aluminium–alumina metal matrix composite coatings using cold spraying and friction stir processing

ABSTRACT This study presents a novel approach for surface repairs of high-strength, cold-worked aluminium (Al) alloys, without negatively affecting the base material strength. Low-pressure cold spraying was used to fabricate Al–Al2O3 metal matrix composite overlays, with varying concentrations of Al2O3 deposited on an Al alloy. Friction stir processing (FSP) was employed to disperse and consolidate the overlay coating on the base material. The FSP was found to improve the Al2O3 particle distribution in the coating and reduce the mean free path between Al2O3 particles. The coating hardness increased after FSP. The post-FSPed overlays also exhibited lower wear rates compared to the as-sprayed condition. Remarkable improvement was observed in the tensile properties of the coatings, which were attributed to the improved dispersion of Al2O3 particles in the matrix, while the enhanced ductility was attributed to the possible grain refinement that occurred due to the recrystallisation of Al during FSP.

Cold sprayed AlNiCoFeCr–TiB2 metal matrix composite coatings

In this work, the mechanically alloyed AlNiCoFeCr high entropy alloy (HEA) was used as matrix to develop metal matrix composite (MMC) coatings. Dense and thick AlNiCoFeCr – 30 wt % TiB2 MMC coatings were firstly fabricated by solid-state cold spraying (CS) technique at the low pressure of 0.9 MPa, and temperature of 300 and 450 °C. The effect of compressed air flow temperature and pressure parameters on structure and mechanical properties of coatings were established. As a low-temperature deposition process, CS completely retained the phase composition and nanostructure in the coatings without any phase transformation. With an increase in pressure up to 0.9 MPa a refinement of the coating structure and a double increase in the fraction of TiB2 particles in the coating were detected. An increase in temperature at least to 300 °C breaks down the oxide layers of the particles, multiplying the deposition efficiency and the properties of the coatings. The coatings fabricated at a spraying temperature of 450 °C and a compressed air flow pressure of 0.9 MPa exhibit the average thickness of 1110 μm, as well as a good combination of high microhardness (6.9 GPa) and sufficient indentation fracture toughness (3.8 MPa∙m1/2).

Microstructure and mechanical properties of SiC-reinforced Inconel 718 composites fabricated by laser cladding

Laser cladding provides the feasibility for fabricating various ceramic-reinforced metal-matrix composite coatings, where the reinforcement content plays a critical role in influencing the residual stresses and the performance of the cladded layer. In this paper, the SiC-reinforced Inconel 718 composites are prepared by LC, and the microstructure and mechanical properties (stress distribution, microhardness, wear behavior) of the cladded layers with different SiC contents are investigated. Based on multi-physics modeling complemented by experimental validation, the thermal stress distribution is analyzed and the residual stresses of the formed Inconel 718/SiC are investigated. The addition of an appropriate amount of SiC can help to relieve residual stresses in the clad layer, with the layer containing 5 wt% SiC corresponding to the minimum residual stress. Moreover, the addition of ceramic particles is conduced to refine the microstructures, and metallic carbides generated by the decomposition of SiC in combination with the diffused elements of the matrix play a positive role in the hardness improvement. The wear resistance of the coatings also increases significantly with increase of SiC content, and the wear mechanism is dominated by abrasive wear, accompanied by oxidation wear, fatigue wear and adhesive wear.

Study of the flexural behaviour and bonding strength of WC-Co metal matrix composite coatings produced by Laser Directed Energy Deposition

Surface coatings enable more durable and sustainable solutions to face the degradation of the functional surfaces of high-added-value components. Particularly, metal matrix composites (MMC) are known to mitigate friction efficiently. However, the bonding strength of MMCs severely limits their durability. Hence, it is not sufficient to focus on wear performance. In this work, the flexural strength and interfacial bonding of Stellite 6/WC MMCs produced by Laser Directed Energy Deposition were investigated. The manufactured coatings exhibited a strong bond to the substrate regardless of the WC content, as no delamination was observed. Additionally, all MMC coatings produced under different processing conditions and with the same composition showed similar elastoplastic behaviour, while specimens containing a higher WC% failed prematurely. This was ascribed to the local embrittlement of the reaction layer surrounding the WC particles, which were found to be crack initiation sites.

Laser Cladding of NiCrBSi/WC + W2C Composite Coatings

This article presents the results of a study on the laser cladding of metal matrix composite coatings using an experimental custom-made powder composed of NiCrBSi matrix with 65 wt.% reinforcing hard particles of eutectic WC + W2C. The chemical and phase composition of the powder was designed to ensure high hardness, abrasion wear resistance at moderate dynamic loads and corrosion resistance at high temperature of the coatings. The influence of the basic processing parameters of the laser cladding, especially energy input, on the quality and single bead geometry, the dilution, share of the massive carbides in the matrix, and the fraction share of reinforcing carbides particles on cross-section of the clads, as well as hardness profiles and abrasive wear resistance, were analysed and presented. The microstructure of test coatings, chemical and phase composition were analysed by optical and scanning electron microscopes (OM, SEM), EDS and XRD spectrometers. It was found that the differences in the wear resistance of the coatings produced at different energy inputs of laser cladding were directly related to the share of the massive carbides WC + W2C in the metal matrix NiCrBSi. The tribological characteristics of the coatings were also studied and described. The test results indicate that the coefficient of friction for carbides is slightly higher than for the metal matrix, and therefore the greater the share of carbides, the higher the value of the coefficient of friction of the coating.

Improvement in comprehensive properties of nanocomposite coatings electro-codeposited with nitride and ceria

Metal matrix composite coatings have attracted scientific and engineering interest because of their excellent mechanical properties. Nano-Si3N4 reinforced nickel coatings with different ceria contents were fabricated by electrodeposition. The microstructures, hardness, and tribological properties as well as corrosion behaviors of the composite coatings were studied in detailed. The results show that incorporation of ceria nanoparticles into the nickel matrix can decrease the grain size and facilitate the (111) texture of the coatings, leading to a smooth surface, compact microstructure, and dispersion-strengthening composites. The 6CeO2 coating with the highest hardness of 520 HV50g demonstrates the best wear resistance, while the 3CeO2 coating shows the best corrosion resistance with the smallest i corr value of 0.0972 μA/cm2. The study suggests a significant improvement in mechanical and anti-corrosion properties by incorporation with the ceria nanoparticles, which has important implications for the surface protection of engineering materials.

Advanced diamond-reinforced metal matrix composite (DMMC) coatings via HVAF process: Effect of particle size and nozzle characteristics on tribological properties

High-velocity air fuel (HVAF) spraying is a versatile and cost-effective platform to fabricate wear resistant coatings. In this work, deposition of Nickel–Phosphorus cladded diamond feedstock is explored as a greener alternative to realize highly wear resistant large-area coatings. To the best of authors knowledge. this is the first study that has utilized HVAF technique for developing wear resistant Ni–P coatings reinforced with diamond (NCD). This work also aims to understand the effect of particle size by using coarse (20–30 μm) and fine NCD (10–15 μm) particles as feedstock. The importance of utilizing appropriate processing conditions was also highlighted by using two different nozzle configurations, for which the two powder particle sizes exhibited considerable differences in terms of microstructure, phase characteristics and mechanical properties. Further, the effect of annealing on the above coating characteristics was also examined, and it is shown that optimal spraying conditions can preclude the need for post-treatment. Furthermore, the as-deposited and annealed coatings were subjected to sliding wear tests to assess their tribological performance. Post-wear analysis performed on worn surfaces revealed the associated wear mechanisms. The results ensuing from this work lay the foundation for realizing new generation of HVAF sprayed wear resistant Ni–P/diamond composite coatings for diverse applications.

Numerical and Experimental Investigations of Cold-Sprayed Basalt Fiber-Reinforced Metal Matrix Composite Coating.

The aluminum-basalt fiber composite coating was prepared for the first time with basalt fiber as the spraying material by cold-spraying technology. Hybrid deposition behavior was studied by numerical simulation based on Fluent and ABAQUS. The microstructure of the composite coating was observed on the as-sprayed, cross-sectional, and fracture surfaces by SEM, focusing on the deposited morphology of the reinforcing phase basalt fibers in the coating, the distribution of basalt fibers, and the interaction between basalt fibers and metallic aluminum. The results show that there are four main morphologies of the basalt fiber-reinforced phase, i.e., transverse cracking, brittle fracture, deformation, and bending in the coating. At the same time, there are two modes of contact between aluminum and basalt fibers. Firstly, the thermally softened aluminum envelops the basalt fibers, forming a seamless connection. Secondly, the aluminum that has not undergone the softening effect creates a closed space, with the basalt fibers securely trapped within it. Moreover, the Rockwell hardness test and the friction-wear test were conducted on Al-basalt fiber composite coating, and the results showed that the composite coating has high wear resistance and high hardness.

A review on Ti-based metal matrix composite coatings

Lightweight high-strength Ti-based metal matrix composites (Ti-based MMCs) have a multitude of application applications, e.g., biomedical engineering, aerospace, and automotive, due to their good sustainability, high specific strength/stiffness, high elevated temperature strength, high wear, and corrosion resistance. Although there are metal matrix composite coatings comprised of polymers, composite, and ceramics materials, the paper primarily focuses on titanium-based composite coatings. This review also discusses the different coating techniques including electrodeposition, thermal spray, plasma spray, vapor deposition, and laser cladding to achieve high hardness and roughness, wear resistance and corrosion resistance. Totally, we attempt to bring out Ti based materials scenario for its current applications.

Effect of Thermochemical Boronizing of Alumina Surface on the Borate Crystals Growth and Interaction with Nickel and Nickel Alloy

Wettability at the metal-ceramic interface is highly important for the development of modern composite materials. Poor wettability by metal melts restricts the use of alumina in protective metal matrix composite (MMC) coatings. In the present experimental study, the possibility to modify wetting properties of alumina by thermochemical surface boronizing was investigated. The results of SEM, EDS, XRD and XPS characterisation of surfaces revealed the formation of oxygen containing Al–B compounds identified as aluminium borates (Al18B4O33/Al4B2O9); no signs of non-oxide Al–B compounds were observed. The shape of the single splats deposited on the boronized alumina surface by the thermal spray and re-melted in the furnace revealed that significant wetting improvement by self-fluxing nickel alloy did not occur. However, the improvement of adhesion between the nickel/nickel alloy and Al2O3 surface was obtained due to formation of an intermediate layer consisting of B, O, Al and Si between the metal and ceramic surfaces at the presence of some silicon at the modified surfaces. The presented study demonstrates that the thermochemical boronizing of alumina in amorphous boron medium is a simple method to obtain a thin aluminium borate layer consisting of oriented nano-rod-like crystals, whose growing direction is predetermined by the orientation of the alumina grains’ faces at surface.

Steam and air oxidation behaviour of thermal spray chromium carbide-based composite coatings

Thermal spray chromium carbide-based composites have been widely used industrially because of their superior oxidation resistance at elevated temperatures compared to other metal matrix composite coatings. In this work, the serviceability of HVOF sprayed coatings from an atomized chromium carbide-based feedstock (Cr23C6-40NiCr) was compared with those from a conventional Cr3C2-25NiCr agglomerated and sintered feedstock. Coatings were exposed to 540 °C and 610 °C for 168 h in both air and steam environments. These conditions are indicative of industrial power plant working conditions to assess their real-time performance. Quantitative Rietveld analysis of the Cr23C6-40NiCr coating XRD patterns indicated a comparable concentration of Cr23C6 in both the powder and coating, implying minimal carbide dissolution. However, the Cr3C2 content in the conventional Cr3C2-25NiCr coating was markedly reduced compared to the initial powder composition, indicating that carbide dissolution occurred to a greater extent. Air oxidation led to the formation of coarse surface oxide, due to the initial formation of Ni-based oxides before a continuous Cr2O3 layer could develop underneath. A notably finer and more uniform oxidized surface composed only of Cr2O3 was formed during steam treatment across both coating types. More importantly, the oxide scale was intact and crack-free in Cr23C6-40NiCr compared to Cr3C2-25NiCr. Moreover, despite Cr23C6 being the main carbide phase and the high binder content (40%NiCr), the microhardness of the Cr23C6-40NiCr coating was comparable to that of the conventional Cr3C2-25NiCr coating, both in the as-sprayed and heat exposed states.