With laser melt injection, metal matrix composite (MMC) layers can be generated on various tools. By using spherical fused tungsten carbide (SFTC) particles as reinforcing material, extremely wear-resistant MMC layers can be produced. However, due to low process speeds, the number of applications for laser melt injection was strongly limited until now. Therefore, a high-speed process for laser melt injection (HSLMI) was developed allowing process speeds up to 100 m/min and an efficient production of tools such as skin-pass rolls, accordingly. Skin-pass rolls are used for setting the final sheet thickness and surface texture. In this paper, new textures for skin-pass rolls generated by HSLMI are presented and characterized. Furthermore, it is studied how the texture of the roll is transferred to the sheet metal. For generating an increased high-low structure, laser ablation was carried out after HSLMI and grinding of the rolls. An analysis of the topography showed that different height differences between SFTC particles and matrix can be set. Furthermore, it was found that all textures were transferred from the roll to the sheet metal.

Cold spray (CS) technology has proven an enormous potential in the production of composite coatings, enabling a production of materials with superior qualities such as enhanced tribological behavior. This study aims to investigate the tribological properties of CS Al-based composite coatings reinforced by quasicrystalline (QC) particles. Two different Al alloys were used as the matrix, AA 6061 and AA 2024, and mixed with Al-based QC particles (Al-Cr-Fe-Cu) at different Al/QC ratios. A room-temperature ball-on-disc test was then used to evaluate the wear resistance of the CS composite coatings in air and compared to those of the CS non-reinforced Al alloy coatings as well as cast counterparts (AA 6061-T6). We have demonstrated that CS could be employed to produce dense and thick Al-QC composites. Further, the addition of the QC particles into the structure increased the wear resistance of the matrix resistance up to 8 times.

This research presents a novel approach for producing metal matrix composite powders using a nanoparticle decoration technique. A 1wt% stable suspension of 30nm Al 2 O 3 particles was decorated onto primary AA6061using a redispersion method. The resulting AA6061-1wt% Al 2 O 3 composite powder was mixed in a rotary mixer for one hour and subsequently dried at 45°C. Scanning electron microscopy of the composite powder confirmed the successful material composition. The composite powders were then deposited onto an AA6061 substrate using a low-pressure cold spray system, with the coating quality, deposition efficiency, surface roughness, and hardness of the deposited materials analyzed. After heat treatment at 430oC, the role of the nanoparticles in hindering recrystallization was studied, with Orowan strengthening shown to be the main mechanism for preventing recrystallization and grain growth. This technique provides a promising alternative method for producing metal matrix composites and offers potential for further exploration of their properties and applications.

Three different coatings were deposited using the Detonation Gun Spraying (DGS) technology from steel powders alone, and steel powers mixed with Fe3C and SiC particles, respectively. The microstructural characteristics of these coatings were examined and the hardness of each type of coating was studied. The morphology and structure of the feedstock powders were affected by the exposure to high temperature during the spraying process and rapid solidification of steel powders that resulted in the formation of an amorphous structure. The unreinforced steel coating had the highest hardness among the three types of coatings, possibly due to a higher degree of amorphization in the coating compared to the other two samples. The microstructural observation confirmed the formation of dense coatings with a layered structure with good connectivity between layers with minimum defects and porosities in the interfacial regions.

Diamond-reinforced composites prepared by cold spray are emerging materials simultaneously featuring outstanding thermal conductivity and wear resistance. Their mechanical and fatigue properties relevant to perspective engineering applications were investigated using miniature bending specimens. Cold sprayed specimens with two different mass concentrations of diamond 20% and 50% in two metallic matrices (Al – lighter than diamond, Cu – heavier than diamond) were compared with the respective pure metal deposits. These pure metal coatings showed rather limited ductility. The diamond addition slightly improved ductility and fracture toughness of the Cu-based composites, having a small effect also on the fatigue crack growth resistance. In case of the Al composites, the ductility as well as fatigue crack growth resistance and fracture toughness have improved significantly. The static and fatigue failure mechanisms were fractographically analyzed and related to the microstructure of the coatings, observing that particle decohesion is the primary failure mechanism for both static and fatigue fracture.

This study developed microstructure-based finite element (FE) models to investigate the behavior of cold-sprayed aluminum-alumina (Al-Al2O3) metal matrix composite (MMCs) coatings subject to indentation and quasi-static compression. Based on microstructural features (i.e., particle weight fraction, particle size, and porosity) of the MMC coatings, representative volume elements (RVEs) were generated by using Digimat software and then imported into ABAQUS/Explicit. State-of-the-art physics-based modelling approaches were incorporated into the model to account for particle cracking, interface debonding, and ductile failure of the matrix. This allowed for analysis and informing on the deformation and failure responses. The model was validated with experimental results for cold-sprayed Al-18 wt.% Al2O3, Al-34 wt.% Al2O3, and Al-46 wt.% Al2O3 metal matrix composite coatings under quasi-static compression by comparing the stress versus strain histories and observed failure mechanisms (e.g., matrix ductile failure). The results showed that the computational framework is able to capture the response of this cold-sprayed material system under compression and indentation, both qualitatively and quantitatively. The outcomes of this work have implications for extending the model to materials design and under different types of loading (e.g., erosion and fatigue).

This paper describes a process that has been developed for producing thick composite coatings with friction and wear properties that were once only achievable in diamond-like carbon (DLC) films. The process is based on cold spraying and the use of surface modified metallic powders. In this investigation, two such powders were prepared by placing either copper or titanium particles on a negatively biased stainless steel tray and then coating them with a DLC film by pulse plasma chemical vapor deposition. The powders are then cold sprayed onto aluminum plates, creating metal-matrix composite coatings. The thickness of the Cu-DLC composite coating is 250 µm and that of the Ti-DLC coating is 435 µm. In each case, the presence of dispersed DLC in the metal matrix was verified by Raman spectroscopy. Sliding wear tests were also conducted, revealing that the Cu-DLC composite has a lower coefficient of friction than copper film, while the Ti-DLC composite has lower specific wear rate than titanium film.

Coatings applied on steel molds used for casting aluminum parts have two main purposes: avoid mold metal reaction and control thermal transfer to obtain directional solidification. The coatings widely known to foundry operators are water-based sodium-silicate bonded ceramic suspensions; they are air sprayed and cured on mold surfaces and typically last for 100 casting cycles. Although thermal sprayed coatings have been shown to last more than 5000 casting cycles, they are not yet the preferred mold protection method. This study addresses the issue by developing a knowledge base of thermal transfer properties that can be achieved with air plasma sprayed magnesium zirconate powders. The properties are assessed on an instrumented mold using the inverse technique for different coating compositions.

Super wear-resistant aluminum-based metal matrix composite (MMC) coatings were produced using cold spraying. Cu-Ni coated diamond and pure diamond particles were used as reinforcing agents. Test results show that the metallic Cu-Ni shell served as a buffer layer, preventing the fracture of diamond particles upon impact as occurred with the uncoated diamond. The coated diamond particles were also found to have a higher deposition efficiency due to metallurgical bonding between the Cu shell and Al matrix. Under tribological testing, all coatings performed well, but those reinforced with the coated diamond showed higher wear resistance due to higher diamond content and involvement of Cu and Ni.

WC-Ni metal-matrix composite coatings were deposited by low-pressure cold spraying using feedstock powders with different amounts of carbide. Uniaxial quasi-static tensile testing was conducted on the as-sprayed coatings to investigate the effect of porosity, particle size, and mean free path on mechanical properties. The evolving strain fields were measured via digital image correlation and image analysis was used to characterize coating microstructure. The coatings with higher carbide content exhibited better tensile properties, which is attributed to significant consolidation of the matrix, increased interfacial area, smaller average carbide size, and reduced mean free path between carbide particles.

Aluminum castings have limited strength and stiffness and tend to exhibit brittle fracture behavior under fatigue loading. These properties can be significantly improved, however, as this study shows, by reinforcing cast aluminum parts with magnesium metal-matrix composite structures. In order to obtain a bond between the cast Al and fiber-reinforced Mg composite surfaces, Al alloy (Al 99 and AlSi 12 ) layers were deposited on the Mg structures by thermal spraying. The mechanical properties of the bonding were assessed via single-lap shear and adhesive tensile tests along with optical microsection analysis. Hybrid aluminum alloy AlSi 10 Mg castings incorporating coated Mg-MMC inserts were also produced and examined, validating the general approach, while revealing that heat input to the MMC structure must be reduced through design or process adaptations.

In this work, advanced Al/diamond wear-resistance composites were fabricated by solid-state cold spray additive manufacturing using core-shell-structured diamond powders. Based on the experimental results and thorough discussion, it is found that core-shell-structured diamond powders were much easier to deposit than pure Al by cold spray, showing great potentials as feedstock for cold spraying. The deposition mechanism of the Al/diamond composites were dominated by the true metallic bonding between Al matrix and Cu layer, which is different from other conventual cold sprayed metal matrix composites. Tensile tests indicated that the tensile strength of the Al/diamond composites can be higher than cold sprayed pure Al. In addition, the Al/diamond composites had super wear-resistance performance. The wear rate was reduced by 17.8 times for the N 4-1 composite and by 37.5 times for the N 1-1 composite as compared with cold sprayed Al/Al 2 O 3 composite.

For fabrication of high strength carbon nanotube (CNT) reinforced Al matrix composites, the uniform dispersion, strong interface bonding and high structural integrity of CNTs have been regard as the three most important issues. In this work, two distinct approaches, namely high shear dispersion (HSD) and shift-speed ball milling (SSBM), were applied to disperse CNTs (1.5 wt.%) into pure Al powders. These two kinds of CNTs/Al composite powders as well as pure Al powders (as comparison) were deposited onto stainless steel plates under the same processing parameters. The deposition efficiency, microstructure, as well as the structural integrity of CNTs in the coatings produced from different starting powders were comparatively investigated. According to the XRD and Raman analysis, the brittle Al 4 C 3 phase was not formed in both CNTs/Al composite coatings. Some structural damages of CNTs were found in both composite coatings, especially the one fabricated from HSD composite powder. The dispersion of CNTs onto Al particle surfaces by HSD approach did not achieve significant strengthening effect on the composite coatings, but adversely affect the metallic bonding of the particles. The microhardness of CNTs/Al composite coating produced from SSBM powders reached to ~115 HV0.1, showing a significant improvement compared to the pure Al coating. The strengthening mechanisms of the cold sprayed CNTs/Al composite coatings were also investigated.

Highly corrosion and wear resistant thermally sprayed chromium carbide (Cr 3 C 2 ) based cermets coatings are nowadays a potential highly durable solution to allow traditional fluidised bed combustors (FBC) to be operated with ecological waste and biomass fuels. However, the heat input of thermal spraying processes causes carbide dissolution in the metal binder. This alters the coating structure and forms carbon saturated amorphous and nanocrystalline metastable areas, which can affect the behaviour of the materials under the corrosive chlorides containing environment of the flue gases. This study analyses the effect of carbide dissolution in the metal matrix of MMC coatings and its effect on the onset of chlorine induced high temperature corrosion. Four Cr 3 C 2 -NiCrMoNb coatings were thermally sprayed with high-velocity air-fuel (HVAF) and high-velocity oxygen-fuel (HVOF) spray processes in order to obtain microstructures with increasing amount of carbide dissolution in the metal matrix. The specimens were heat treated in an inert argon atmosphere at 700°C for 5 hours to induce secondary carbide precipitation. As-sprayed and heat-treated self-standing coatings were covered with KCl and their corrosion resistance was investigated with thermogravimetric analysis (TGA) at 550°C for 4 hours. High carbon dissolution in the metal matrix appeared to be a detrimental factor in the initial stage of corrosion. The microstructural changes induced by the heat treatment hindered the corrosion onset in the coatings. Moreover, an optimal amount of oxides and melting degree seemed beneficial.

In this study abrasive wear resistance of NiCrBSi self-fluxing alloys claddings reinforced by tungsten carbide (up to 80 vol.%) and pure tungsten (up to 50 vol.%) was compared. For this purpose, metal matrix composite samples were cladded by diode laser then metallography studies and hardness measurements were provided. Finally, all specimens passed ASTM G65 abrasion test and their wear resistance was compared to alternatives claddings.

Low-pressure cold spray has been used as an innovative method to deposit metal matrix composite (MMC) coatings: boron carbide-nickel (B4C-Ni) and tungsten carbide-cobalt-nickel (WC-Co-Ni) composites. The coatings were studied using scanning electron microscopy, X-ray diffraction with Rietveld refinement, and acoustic emission-coupled four-point flexural test. Indentation fracture toughness tests were performed on the WC-Co-Ni coatings, only. The results showed that the composites had reinforcing particle volume fractions of 45.8 ± 0.3 vol.% and 22.7 ± 0.1 vol.% for the WC-Co-Ni and B4C-Ni MMC coatings, respectively. Flexural tests were used to evaluate the fracture strain of the composites. In these tests, the WC-Co-Ni composite failed by brittle facture at approximately 0.5% nominal strain. The B4C-Ni composite showed flexural behaviour similar to that of an unreinforced Ni matrix. These results suggest that there was insufficient B4C within the coating to affect significantly the ductile failure mode of Ni matrix. Post bending fracture analysis showed the presence of straight, continuous cracks on the WC-Co-Ni surface and the indentation fracture toughness of WC-Co-Ni was found to be 1.2 ± 0.2 MPa·m0.5. Discontinuous, random cracks were observed on the B4C-Ni surface. The quantification of these properties is essential in evaluating the performance of the low-pressure cold sprayings to determine their potential applications.

NiCrBSi is a material generally used in wear-resistant coatings. In order to improve the tribological properties of atmospheric plasma-sprayed NiCrBSi coatings, Molybdenum (Mo) was incorporated into the NiCrBSi coatings to reduce the friction coefficient and wear rate under dry and oil-lubricated conditions. In this paper, Mo-NiCrBSi composite coatings with Mo content of 5, 10, 20 and 30 wt.% were deposited on stainless steel substrates respectively by atmospheric plasma spray. X-ray diffraction, optical microscopy and scanning electron microscopy equipped with energy dispersive spectroscopy were utilized to investigate the phase structure and surface morphology of the composite coatings. Reciprocating friction tests were conducted to measure the friction coefficients and 3D optical microscopy was used to depict the wear track profiles. The results showed that the 30 wt.% Mo-NiCrBSi coating exhibits the best tribological performance. In addition, MoO 2 and MoS 2 films were formed in the friction process under dry condition and oil-lubricated condition respectively.

B 4 C-Ni powders ranging in content from 5-60 wt% Ni were fabricated by pressurized hydrogen reduction and deposited on mild carbon steel substrates by air plasma spraying. The microstructure, morphology, and phase composition of the powders and coatings were evaluated by means of SEM and XRD analysis. The influence of Ni content on coating microstructure, fretting wear resistance, hardness, and adhesive strength was investigated in detail. The results show that Ni affects fretting wear resistance, which was found to be highest in the coating with 40 wt% nickel. The B 4 C-40Ni coating also proved superior in terms hardness, porosity, and friction coefficient, although its adhesive strength was the lowest.

Diamond-reinforced copper matrix composites (DCMC) have great potential for heat sink applications due to their excellent thermal properties. In this investigation, thick DCMC coatings were fabricated via cold spraying using copper-clad diamond powder or its mixture with copper powder. With pure clad diamond powder, the diamond in the original feedstock was almost completely retained in the coating, which contained more than 40 wt% diamond. With mechanically mixed clad diamond and Cu powder, the diamond fraction in the coating was even larger than that of the original feedstock. It was found that the added Cu powder acts as a buffer, effectively preventing the fracture of diamond in the coating.

This study evaluates the possibility of depositing hard B 4 C and TiC reinforcing particles in a Ni matrix using low-pressure cold spraying. It also investigates the effect of particle velocity and kinetic energy on deposition efficiency, microstructure, hardness, and wear resistance. B 4 C and TiC powders were blended at 50, 75, and 92 wt% carbide content with Ni powder comprising the remainder of the mixture. The impact velocity of sprayed carbide particles was calculated using a mathematical model based on the thermodynamics of compressible fluid flow through a converging-diverging nozzle. The model showed that the kinetic energy of TiC particles prior to impact was three times smaller than that of B 4 C, resulting in a higher carbide content (18 wt% compared to 8 wt%) due to reduced fracture and rebound of the TiC particles. Although the hardness values of both coatings are within the range of cold-sprayed WC-Co-Ni, wear rates were found to be high.