Metal Matrix Composite Coatings Research Articles

Characterization of Cr–ZrO2 composite coatings electrodeposited from Cr(III) bath

The aim of this work was to incorporate ZrO2 particles into a Cr matrix within the research work aimed at obtaining metal matrix composite coatings (Cr–ZrO2) under direct current and to evaluate their protective properties. A Cr–ZrO2 composite coating was deposited from an electrolyte based on trivalent chromium sulphate with formate-urea as a complexing agent containing various concentrations of ZrO2. Cross-section investigations have revealed that ZrO2 particles incorporated into the Cr coating are uniformly distributed. The results indicate that ZrO2 particles influence the microhardness, morphology and corrosion behaviour of Cr–ZrO2 composite coatings obtained from the Cr(III) bath.

Metal Matrix Composite Coatings of Cupronickel Embedded with Nanoplatelets for Improved Corrosion Resistant Properties

The deterioration of metals under the influence of corrosion is a costly problem faced by many industries. Therefore, particle-reinforced composite coatings are being developed in different technological fields with high demands for corrosion resistance. This work studies the effects of nanoplatelet reinforcement on the durability, corrosion resistance, and mechanical properties of copper-nickel coatings. A 90 : 10 Cu-Ni alloy was coelectrodeposited with nanoplatelets of montmorillonite (Mt) embedded into the metallic matrix from electrolytic baths containing 0.05, 0.10, and 0.15% Mt. X-ray diffraction of the coatings indicated no disruption of the crystal structure with addition of the nanoplatelets into the alloy. The mechanical properties of the coatings improved with a 17% increase in hardness and an 85% increase in shear adhesion strength with nanoplatelet incorporation. The measured polarization resistance increased from 11.77 kΩ·cm2for pure Cu-Ni to 33.28 kΩ·cm2for the Cu-Ni-0.15% Mt coating after soaking in a simulated seawater environment for 30 days. The incorporation of montmorillonite also stabilized the corrosion potential during the immersion study and increased resistance to corrosion.

Cold‐Sprayed Metal Coatings with Nanostructure

Cold spray is a solid‐state coating deposition technology developed in the 1980s. In comparison with conventional thermal spray processes, cold spray can retain the original properties of feedstock, prevent the adverse influence on the underlying substrate materials, and produce very thick coatings. Coatings with nanostructure offer the potential for significant improvements in physical and mechanical properties as compared with conventional non‐nanostructured coatings. Cold spray has also demonstrated great capability to produce coatings with nanostructure. This paper is aimed at providing a comprehensive overview of cold‐sprayed metal coatings with nanostructure. A brief introduction of the cold spray technology is provided first. The nanocrystallization phenomenon in the conventional cold‐sprayed metal coatings is then addressed. Thereafter, focus is switched to the microstructure and properties of the cold‐sprayed nanocrystalline metal coatings, and the cold‐sprayed nanomaterial‐reinforced metal matrix composite (MMC) coatings. At the end, summary and future perspectives of the cold spray technology in producing metal coatings with nanostructure are concluded.

Abrasive jet system and its various applications in abrasive jet machining, erosion testing, shot-peening, and fast cleaning

Abrasive jet system is one of the effective tools and found several present and future applications in many manufacturing industries and R&D sectors. In the form of abrasive jet it is used for machining like cutting, drilling, and engraving of brittle materials. Surface fast cleaning and preparation are done by using abrasive jet for welding and plasma spray coatings. The erosion tests of turbine blades, propellers are done by using abrasive jet application. Some special type of particles are used for shot peening for surface hardening. An abrasive jet system is in-house designed and manufactured and its performance is observed in various applications like machining, cleaning, and erosion tests. In this present research work, a critical review has been done on various applications of abrasive jet systems. Based on the present status of work, the application possibilities of the present abrasive jet system is experimentally evaluated. It is evident that the abrasive jet system using natural sand can be used for cutting, drilling and engraving of brittle material like glass, marble, etc. Rust cleaning from the metal surface and erosion tests of metal matrix composite laser coatings are also performed by using the same abrasive jet system.

Mechanical and tribological performance of a hybrid MMC coating deposited on Al-17Si piston alloy by laser composite surfacing technique.

Laser composite surfacing (LCS) is a photon driven manufacturing technology that can be utilized for depositing hybrid metal matrix composite coatings (HMMC) on softer Ti/Al/Mg alloys to enhance their tribo-mechanical properties. LCS offers the advantages of higher directionality, localized microstructural refinement and higher metallurgical bonding between coating and substrate. The current research presents the tribo-mechanical evaluation and characterization of solid lubricant based Ni–WC coatings deposited by LCS on Al–Si piston alloy by varying the concentration of graphite between 5-to-15-weight percentage. The tribological behavior of LCS samples was investigated using a ball-on-plate tribometer. Results indicate that the surface hardness, wear rate and friction coefficient of the Al–Si hypereutectic piston alloy were improved after LCS of graphite based HMMC coatings. The maximum surface hardness of 781Hv was acquired for the Ni–WC coating containing 5 wt% graphite. The friction coefficient of Al–Si under dry sliding conditions was reduced from 0.47 to 0.21. The reduction in the friction coefficient was attributed to the formation of a shearable transfer layer, which prevented delamination and reduced adhesion, abrasion and fatigue cracking.

Influence of exposure at high temperature on the local scratch mechanisms in laser cladded Inconel 625-base metal matrix composite coatings

The mechanisms that characterise the local scratch behaviour of the matrix of an IN625-Cr3C2 composite coating were determined and compared with those of the same Inconel alloy clad. The study was performed for both the coatings in the as-deposited condition and after high-temperature exposure. The coatings were deposited by laser cladding. Scratch tests with a Berkovich sharp indenter were carried out on the surface of the coatings. A model to calculate the volume displaced during the scratch tests was proposed, and the contributions of the four main mechanisms that describe the local scratch behaviour were investigated. The analysis of the results showed that microploughing characterises the IN625 clads behaviour. The formation of M7C3 carbides in the composites' matrix, arising from the partial fusion of the Cr3C2 particles during the deposition, transform the main scratch mechanism into a microcutting process. After exposure at high temperature, microploughing continues to be the main mechanism that describes the IN625 behaviour, but the formation of secondary phases constrains the plastic deformation, increasing the scratch resistance. The behaviour of the composite matrix was affected only by the exposure at the highest temperatures where the local scratch resistance results increased and microcutting remained the most important mechanism.

Effect of Impact Angle on Ceramic Deposition Behavior in Composite Cold Spray: A Finite-Element Study

During the cold spraying of particle-reinforced metal matrix composite coatings (ceramic and metal particles mixture) on metal substrates, ceramic particles may either get embedded in the substrate/deposited coating or may rebound from the substrate surface. In this study, the dependence of the ceramic rebounding phenomenon on the spray angle and its effect on substrate erosion have been analyzed using finite-element analysis. From the numerical simulations, it was found that the ceramic particle density and substrate material strength played the major roles in determining the embedding and ceramic retention behavior. Substrate material erosion also influenced the ceramic retention, and the material loss increased as the impact angles decreased from normal. In general, the results concluded that decreasing the impact angle promoted the retention possibility of ceramics in the substrate. This study provides new theoretical insights into the effect of spray angles on the ceramic retention and suggests a new route toward optimizing the spraying process to increase the ceramic retention in composite coatings cold spray.

Fabrication and Characterization of Ni-SiC Nanocomposite Coatings on Al Substrates by Ball Impact Deposition Method

Micron-size Ni and SiC powder mixtures were used to prepare Ni-SiC nanocomposite coatings on an Al substrate by employing a high-energy ball milling technique. Ni:SiC weight ratio was varied over a wide range to explore the effect of the charge composition on the microstructure, composition, microhardness, and wear properties of the depositions. It was observed that the composition of the produced coating was correlated to the charge composition in a complex manner, which suggests that deposition rates for Ni and SiC particles significantly vary depending on the charge composition; SiC deposition rate was higher than that of Ni when Ni:SiC weight ratio was greater than 3:1. Diffusion of Al from the substrate into the Ni matrix provided evidence for the metallurgical bonding at the interface. Both microstructural and mechanical properties of the produced coatings were found to be crucially dependent on the charge composition. By increasing the SiC content in the charge from about 5 to 33 wt pct, the mechanical properties enhanced due to the dispersion strengthening effect of the incorporated SiC particles in the coatings and the crystallite size of the Ni matrix decreasing to the nanometer range. However, a further increase resulted in the formation of a coating with a poor degree of compaction. It was found that the composite coating with about 15 vol pct SiC, produced from the charge with Ni:SiC weight ratio of 2:1, showed a microhardness as high as 830 HV0.05 along with excellent wear resistance. Despite the current sample size limitations for applying high-energy ball milling, the present findings demonstrate that the adopted technique holds good prospect for the synthesis of nanostructured metal matrix composite coatings with enhanced and tunable properties.

Effect of type of reinforcing particles on the deposition efficiency and wear resistance of low-pressure cold-sprayed metal matrix composite coatings

Low-pressure cold spraying was used to deposit boron carbide (B4C), titanium carbide (TiC), and tungsten carbide (WC) based metal matrix composite (MMC) coatings. Nickel (Ni) was used as the matrix and each carbide powder was mechanically blended with Ni powder prior to spraying. The average velocity of the carbide particles and their momentum during the cold spray deposition were estimated using a mathematical model. The effect of the carbide particle momentum on the Vickers micro-hardness and wear resistance was evaluated. The model showed that the average momentum of WC particles was more than two times greater than that of B4C particles and almost six times greater than that of TiC particles. The higher momentum of the WC particles led to a higher level of work hardening of the matrix, which resulted in improvement of the hardness and wear resistance of the MMC coatings. This led to similar hardness values for the deposited MMC coatings (400kg/mm2) despite the difference in hardness of the selected reinforcing carbides. Furthermore, it was found that the high momentum and high fracture toughness of the WC particles increased the roughness of the coating surface and compacted the coating, which led to higher deposition efficiency for this carbide-metal powder blend on previously deposited coating layers. The lowest wear resistance was achieved by the WC-Ni MMC coatings due to the higher fracture toughness of WC particles and also work hardening of the Ni matrix. The results obtained emphasize the importance of the carbide fracture toughness and particle momentum on the deposition efficiency, hardness, and wear resistance of cold-sprayed MMC coatings.

Effect of Surface Roughness and Structure Features on Tribological Properties of Electrodeposited Nanocrystalline Ni and Ni/Al2O3 Coatings

Metal matrix composite coatings obtained by electrodeposition are one of the ways of improving the surfaces of materials to enhance their durability and properties required in different applications. This paper presents an analysis of the surface topography, microstructure and properties (residual stresses, microhardness, wear resistance) of Ni/Al2O3 nanocomposite coatings electrodeposited on steel substrates from modified Watt’s-type baths containing various concentrations of Al2O3 nanoparticles and a saccharin additive. The residual stresses measured in the Ni/Al2O3 coatings decreased with an increasing amount of the co-deposited ceramics. It was established that the addition of Al2O3 powder significantly improved the coatings’ microhardness. The wear mechanism changed from adhesive-abrasive to abrasive with a rising amount of Al2O3 particles and coating microhardness. Nanocomposite coatings also exhibited a lower coefficient of friction than that of a pure Ni-electrodeposited coating. The friction was found to depend on the surface roughness, and the smoother surfaces gave lower friction coefficients.

Online assessment of TiC decomposition in laser cladding of metal matrix composite coating

Decomposition of ceramic particles in metal matrix composite coatings developed by laser cladding process is one of the major problems that deteriorate the mechanical properties of coating. Further, a large number of process parameters involved in laser cladding makes the process optimization difficult. Therefore, a study was undertaken to assess the condition of TiC particles in the molten pool by monitoring the thermal history using an IR pyrometer. It was observed that with the increase of molten pool lifetime, a reaction layer is created between TiC particles and metal matrix which improves their bonding. However, with further increase in the molten pool lifetime TiC particles were found to decompose completely forming dendritic structure in the metal matrix through heterogeneous nucleation and subsequent crystallization during the solidification process. This results in a change of the solidification shelf slope which can be used as an effective signature to assess the TiC particle condition in molten pool online without performing any destructive test. The modified structure of metal matrix exhibited brittle nature which increased the wear rate due to fracture and spalling of coating during the wear test.

Tribological Properties of Functionally Graded Ni-Al2O3 Nanocomposite Coating

The main challenge in producing metal matrix composite coatings is achieving a homogeneous distribution of the second phase particles and avoiding the particle agglomeration. Despite all the works done up to now, the effect of the particles’ distribution in the matrix of composite coatings on the tribological properties has rarely been reported. The primary concern of the present study is to investigate the tribological behavior of functionally graded nickel-Al2O3 nanocomposite coating produced at different duty cycles in 3.5%wt NaCl solution. Before starting the tribocorrosion test, the open circuit potential variations are small and reached stable values which followed by a negative shift during and after the tribocorrosion test. SEM and EBSD images showed that by decreasing the duty cycle the width of the wear track decreased because of more incorporated particles and changing of the (001) structure to compact random texture. Although the EIS results show the corrosion resistance decreased by increasing the embedded particles, higher hardness and compact structure result in better tribocorrosion properties of samples prepared at lower duty cycle. The adhesive wear was the dominant mechanism for coatings plated at high duty cycle and it changed to the abrasive wear in sample prepared at lower duty cycle.

Wear resistance in the soil of Stellite-6/WC coatings produced using laser cladding method

The paper presents the study results of macro- and microstructure, microhardness, phase composition and practical application of Stellite-6/WC metal matrix composite (MMC) coatings produced using laser cladding technology. For the preparation of MMC coatings the Yb:YAG disc laser with a rated power equal 1kW was used. The laser beam was controlled using a 5-axis CNC machine. The powder mixture was fed to laser beam by three-streams powder feeding system. Composite coatings were prepared to increase the durability of agricultural tools. The coatings were prepared on B27 boron steel. This steel grade is most often used into produce the tools for soil cultivation. Stellite-6/WC coatings were produced using laser beam power 550W, feed rate 400mm/min and powder feed rate 10g/min. Durability tests of agricultural tools were carried out by two methods. Measurement the mass loss was the first method, while measurement the tools shape using GOM ATOS II optical scanner was the second method. It was found that Stellite-6/WC coatings contributed to increase durability of agricultural tools applied for soils cultivation.

The erosion performance of cold spray deposited metal matrix composite coatings with subsequent friction stir processing

This study forms an initial investigation into the development of SprayStir, an innovative processing technique for generating erosion resistant surface layers on a chosen substrate material. Tungsten carbide – cobalt chromium, chromium carbide – nickel chromium and aluminium oxide coatings were successfully cold spray deposited on AA5083 grade aluminium. In order to improve the deposition efficiency of the cold spray process, coatings were co-deposited with powdered AA5083 using a twin powder feed system that resulted in thick (>300μm) composite coatings. The deposited coatings were subsequently friction stir processed to embed the particles in the substrate in order to generate a metal matrix composite (MMC) surface layer. The primary aim of this investigation was to examine the erosion performance of the SprayStirred surfaces and demonstrate the benefits of this novel process as a surface engineering technique. Volumetric analysis of the SprayStirred surfaces highlighted a drop of approx. 40% in the level of material loss when compared with the cold spray deposited coating prior to friction stir processing. Micro-hardness testing revealed that in the case of WC-CoCr reinforced coating, the hardness of the SprayStirred material exhibits an increase of approx. 540% over the unaltered substrate and 120% over the as-deposited composite coating. Microstructural examination demonstrated that the increase in the hardness of the MMC aligns with the improved dispersion of reinforcing particles throughout the aluminium matrix.

The erosion performance of particle reinforced metal matrix composite coatings produced by co-deposition cold gas dynamic spraying

This work reports on the erosion performance of three particle reinforced metal matrix composite coatings, co-deposited with an aluminium binder via cold-gas dynamic spraying. The deposition of ceramic particles is difficult to achieve with typical cold spray techniques due to the absence of particle deformation. This issue has been overcome in the present study by simultaneously spraying the reinforcing particles with a ductile metallic binder which has led to an increased level of ceramic/cermet particles deposited on the substrate with thick (>400μm) coatings produced. The aim of this investigation was to evaluate the erosion performance of the co-deposited coatings within a slurry environment. The study also incorporated standard metallographic characterisation techniques to evaluate the distribution of reinforcing particles within the aluminium matrix. All coatings exhibited poorer erosion performance than the uncoated material, both in terms of volume loss and mass loss. The Al2O3 reinforced coating sustained the greatest amount of damage following exposure to the slurry and recorded the greatest volume loss (approx. 2.8mm3) out of all of the examined coatings. Despite the poor erosion performance, the WC-CoCr reinforced coating demonstrated a considerable hardness increase over the as-received AA5083 (approx. 400%) and also exhibited the smallest free space length between adjacent particles. The findings of this study reveal that the removal of the AA5083 matrix by the impinging silicon carbide particles acts as the primary wear mechanism leading to the degradation of the coating. Analysis of the wear scar has demonstrated that the damage to the soft matrix alloy takes the form of ploughing and scoring which subsequently exposes carbide/oxide particles to the impinging slurry.

Super hard WC-Cr composite coatings: An approach to potential wear applications

Abstract In this study, submicron (APS = 200 nm) tungsten carbide (WC) ceramic particles were co-deposited with chromium metal (Cr) via electro-co-deposition system to fabricate WC-Cr metal matrix composite coatings. Instead of traditional electrodeposition cells, a new system was designed and coatings were fabricated using this system. Phase identifications of the coatings were performed by X-ray diffractometry (XRD) and surface morphologies were investigated using energy dispersive X-ray spectroscopy (EDS) with attached scanning electron microscope (SEM). Hardness values of the coatings were performed under 980.7 mN applied load using a microhardness tester. It was concluded that WC ceramic particles were physically adsorbed on the cathode surface and formed a composite structure with metal Cr and co-deposition of submicron sized ceramic particles with metals via electrodeposition system was strictly successful. In addition, with respect to the reference coatings, WC reinforced composite coatings depict an increased hardness up to twice its value. Frequency, as a parameter of pulse current, is determined as an effective parameter in co-deposition.

Strengthening mechanism and metal/ceramic bonding interface of cold sprayed TiNp/Al5356 deposits

As the literature reported, the microhardness of particle reinforced metal matrix composite coatings fabricated by cold spraying (CS) could be significantly increased compared to pure metallic coatings by CS. However, the correlation between the strengthening mechanism of reinforcements and the microhardness increment is still not well revealed. Therefore, in this study, two strengthening mechanisms of reinforcement particles in CSTiNp/Al5356 coatings, i.e. the strain hardening effect of reinforcement particles tamping on the metal matrix and the dispersion strengthening effect of uniformly dispersed reinforcement particles, were studied, and the proportions by two strengthening effects were qualitatively characterised as a first approximation by a proposed microhardness calculation model based on the hardness data of both the as sprayed and heat treated coatings. Results show that the dispersion strengthening effect of TiN particles plays a greater role in microhardness increment than the strain hardening effect of TiN tamping on the Al5356. In addition, the bonding interface of metal/ceramic particles in TiNp/Al5356 coatings was characterised using a transmission electron microscope for revealing the bonding features at the interface. Results show that although an intimate contact (i.e. bonding) is formed at the TiNp/Al5356 interface, the bonding is relatively weak, with some cracks or pores possibly present at the interface.

Direct Diode Laser Cladding of Inconel 625/WC Composite Coatings

Metal matrix composite coatings, composed of Inconel 625 alloy and tungsten carbide (WC), have been produced by laser cladding using a high power direct diode laser with a rectangular laser beam spot and a top-hat beam profile. The primary goal of the investigation was to understand the role of the shape of WC particles and the heat input level on the quality of the composite coating system used, especially on its erosion behaviour. The results indicated that angular WC particles are more susceptible to dissolution in the molten pool than spherical. However, the composite coatings containing angular WC particles exhibited significantly higher erosion resistance than those with spherical WC for both normal and oblique impacts. This is directly attributed to the excellent mechanical interlocking of the angular WC in the matrix. The WC/matrix interfacial decohesion has been observed in the coatings containing spherical WC at the oblique impact.

Dendrite Suppression by Shock Electrodeposition in Charged Porous Media.

It is shown that surface conduction can stabilize electrodeposition in random, charged porous media at high rates, above the diffusion-limited current. After linear sweep voltammetry and impedance spectroscopy, copper electrodeposits are visualized by scanning electron microscopy and energy dispersive spectroscopy in two different porous separators (cellulose nitrate, polyethylene), whose surfaces are modified by layer-by-layer deposition of positive or negative charged polyelectrolytes. Above the limiting current, surface conduction inhibits growth in the positive separators and produces irregular dendrites, while it enhances growth and suppresses dendrites behind a deionization shock in the negative separators, also leading to improved cycle life. The discovery of stable uniform growth in the random media differs from the non-uniform growth observed in parallel nanopores and cannot be explained by classic quasi-steady “leaky membrane” models, which always predict instability and dendritic growth. Instead, the experimental results suggest that transient electro-diffusion in random porous media imparts the stability of a deionization shock to the growing metal interface behind it. Shock electrodeposition could be exploited to enhance the cycle life and recharging rate of metal batteries or to accelerate the fabrication of metal matrix composite coatings.

Multiresponse Optimization of Laser Cladding Steel + VC Using Grey Relational Analysis in the Taguchi Method

Laser cladding of metal matrix composite coatings (MMCs) has become an effective and economic method to improve the wear resistance of mechanical components. The clad quality characteristics such as clad height, carbide fraction, carbide dissolution, and matrix hardness in MMCs determine the wear resistance of the coatings. These clad quality characteristics are influenced greatly by the laser cladding processing parameters. In this study, American Iron and Steel Institute (AISI) 420 + 20% vanadium carbide (VC) was deposited on mild steel with a high powder direct diode laser. The Taguchi-based Grey relational method was used to optimize the laser cladding processing parameters (laser power, scanning speed, and powder feed rate) with the consideration of multiple clad characteristics related to wear resistance (clad height, carbide volume fraction, and Fe-matrix hardness). A Taguchi L9 orthogonal array was designed to study the effects of processing parameters on each response. The contribution and significance of each processing parameter on each clad characteristic were investigated by the analysis of variance (ANOVA). The Grey relational grade acquired from Grey relational analysis was used as the performance characteristic to obtain the optimal combination of processing parameters. Based on the optimal processing parameters, the phases and microstructure of the laser-cladded coating were characterized by using x-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS).