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Abstract: High-entropy alloys have been found to have novel microstructures and unique properties. The main method of manufacturing is vacuum arc remelting. As in situ cladding laser cladding has capability of achieving a controllable dilution ratio, fabricating highentropy alloy by laser cladding is of great significance and potential for extensive use. In this study, a novel AlxFeCoNiCuCr high-entropy alloy system was manufactured as the thin layer of the substrate by laser cladding; also high temperature hardness, abrasion performance, corrosion nature of the AlxFeCoNiCuCr high-entropy alloy were tested under the different ratio of aluminum. This study shows higher aluminum clad exhibit higher hardness, better abrasion resistance and corrosion resistance. [Copyright &y& Elsevier]

Abstract: WC/Ni coating was formed by laser cladding of a W/C/Ni powder blend. The formed WC crystals have rectangular or quadrangle cross-section shapes with size of 2–30μm. Step, twist and cross growth morphologies of WC formation were observed. The coating contains WC, CW3, WNi, FeW3C, Fe6W6C, W3O, W, C, and (Fe,Ni) phases. [Copyright &y& Elsevier]

Abstract: In order to improve wear resistance of aluminum alloy, the in situ synthesized TiB2 and Ti3B4 peritectic composite particulate reinforced metal matrix composite formed on the 2024 aluminum alloy by laser cladding with a powder mixture of Fe coated Boron, Ti and Al was successfully achieved using 3 kW CW CO2 laser. The laser cladding coating present excellent bonding with aluminum alloy substrate. The chemical composition, microstructure and phase structure of the composite clad coating were analyzed by energy dispersive X-ray spectroscopy (EDX), SEM and XRD. The typical microstructure of composite coating is composed of TiB2, Ti3B4, Al3Ti, Al3Fe and α-Al. The surface hardness of cladding coating is increased with the amount of added Fe coated B and Ti powder which determines the amount of TiB2 and Ti3B4 peritectic composite particulate, and obviously higher than that of substrate. The wear tests were carried out using a FALEX-6 type pin-on-disc machine. The test results show that the composite coatings with the in situ synthesized TiB2 and Ti3B4 peritectic improve wear resistance when compared with the as-received Al substrate. [Copyright &y& Elsevier]

Abstract: A PRC-3 kW continuous wave CO2 laser was used to clad a MoS2/TiC/Ni coatings on the surface of a 1045 low carbon steel substrate. The microstructure and phase composition of the composite coating were studied. The typical microstructure of the composite coating is composed of multi-sulfide phases including binary element sulfides, ternary element sulfides, Ni, TiC and Mo2C. Wear tests were carried out using a FALEX-6 type pin-on-disc machine. The results showed that the MoS2/Ni coating (as a contrasted sample) exhibited the lowest friction coefficient and the largest weight loss in comparison to other investigated specimens. The friction coefficient of the MoS2/TiC/Ni coating is lower than that of quenched 45 steel and weight loss is only one-sixth of that of 45 steel. The worn surface of MoS2/TiC/Ni laser cladding coating is so clean and smooth (no noticeable groove and scratches visible) that the microstructure of coating is identified after dry wear test of 40 min. [Copyright &y& Elsevier]

Abstract: In order to improve the wear resistance of an aluminum alloy, an in situ synthesized TiB2 particulate-reinforced metal matrix composite coating was formed on a 2024 aluminum alloy by laser cladding with a powder mixture of Fe-coated boron, Ti and Al was successfully achieved using a 3-kW CW CO2 laser. The chemical composition, microstructure and phase structure of the composite clad coating were analyzed by energy dispersive X-ray spectroscopy (EDX), SEM, TEM and XRD. The nanohardness and the elastic modulus of the phases of the coating have been examined. The dry sliding wear behaviour of the coating was investigated using a pin-on-ring machine under four loads, namely 8.9, 17.8, 26.7, and 35.6N. It has been found that the wear characteristics of cladding were completely dependent on the content and morphology of the TiB2 particulate and intermetallic in the microstructure and the applied load. At the lowest load (8.9N), with increasing content of TiB2 particulate and intermetallic, the wear weight loss of the laser cladding was decreased. At higher loads (17.8, 26.7, and 35.5N), the 2024 Al alloy exhibited superior wear resistance to the particle-reinforced metal matrix composite cladding. [Copyright &y& Elsevier]

Detailed experiments have been conducted to produce a nickel-based alloy composite coating reinforced with TiC particles on medium carbon steel substrate by powder feeding laser cladding using a coaxial nozzle. The chemical compositions, microstructures and surface morphology of the coatings were analyzed using scanning electron microscopy (SEM), energy disperse X-ray spectroscopy (EDS) and X-ray diffractometry (XRD). Composite coatings with TiC particles of various shapes and sizes embedded in nickel-based alloy were synthesized in-situ during laser processing. An excellent bonding between the coating and the carbon steel substrate was obtainable. The coatings were uniform, continuous and free from cracks. The microstructure of the coating was mainly composed of γ-Ni dendrites, a small amount of CrB, Ni3B, M23C6 and dispersed TiC particles. The maximum microhardness of the coating was about HV0.21200. [Copyright &y& Elsevier]

Various weight ratios of TiC particulate nickel-based composite coatings were produced on carbon steel substrates by laser cladding. The experimental results showed that the coating was uniform, continuous and free of cracks when a CaF2 flux was used. Excellent bonding between the coating and the medium carbon steel substrate was ensured by the strong metallurgical interface. The microstructures of the coating were mainly composed of γ-Ni dendrites, M23C6, a small amount of CrB, and dispersed TiC particles. The morphologies of TiC particles changed from the globular, cluster to flower-like shape. The volume fraction of TiC particles and the microhardness gradually increased from the bottom to the top of the coating, and the volume fraction of TiC particles increased with increasing of volume fraction of Ti and C. The maximum microhardness of the coatings with 10, 15 and 20 wt.% (Ti+C) in the preplaced alloy powder was approximately HV0.2750, HV0.2850 and HV0.2920, respectively, which was much larger than that of the steel substrate, HV0.2240. [Copyright &y& Elsevier]

In order to improve resistance to high temperature and wear resistance of pure aluminum, laser-cladding experiments were conducted on a 3 kW continuous wave CO2 laser to produce in situ synthesized molybdenum silicide (MoSi2)/SiC composite coatings on pure aluminum. The laser consolidified microstructure and phase evolution were investigated using scanning electron micrograph and X-ray diffraction (XRD). The in situ formation of MoSi2/SiC was carried out by adding a mixture of Mo, Si and C precursor powder layer followed by melting the layer and substrate under a laser beam. The experimental results showed that these compounds, MoSi2 and SiC, can be formed from three distinct powders of Mo, Si and C on Al alloy, and, provided that supplied energy is sufficient to start the reaction between the initial products, a good metallurgical bond between coating and the substrate can be achieved. The microstructures of the coating were composed of MoSi2, Mo5Si3 and SiC phases. The microhardness of coating was about 12 times that of the aluminum substrate, the maximum value reached HV0.2 1200. [Copyright &y& Elsevier]

A composite coating with TiC particles of various shapes and sizes embedded in nickel based alloy has been in situ synthesized by laser melting a precursor mixture of nickel based alloy powder, graphite and titanium powders. The experiment result showed that the coating epitaxially grew from the substrate with excellent bonding between the coating and the carbon steel substrate. The coating is uniform, continuous and free of pores and cracks, and about 0.6 mm thick. The microstructure of the coating is mainly composed of γ-Ni dendrite, a small amount of interdendritic (γ-Ni+M23C6) eutectic, and dispersed TiC particles. The volume fraction of TiC particles and the microhardness gradually increased from the bottom to the top of the coating layer. [Copyright &y& Elsevier]

Abstract: Fabrication of nanoporous Cu–Mn alloy coatings was investigated by a two-step process involving high power laser cladding of a homogeneous Cu40Mn60 alloy coatings followed by selectively electrochemical de-alloying. Auger mapping results indicate that nanoporous manganese was obtained by selective electrochemical etching of the less active Cu component owing to the passivation of the more active manganese in potassium nitrate solution. The surface morphology of the porous Mn was a ribbon-like structure, different from interconnected bicontinuous nanopores that are usually obtained by de-alloying. The influence of de-alloying time, electric potential and temperature on the formation of nanoprosity is systematically investigated. Nanopore sizes can be tailored to be less than 100nm. Under optimal etching conditions the nanopore size was below 25nm. The surface area of the nanoporous manganese layer was enhanced by up to 990 times compared with that of a polished sample. [ABSTRACT FROM AUTHOR]

Abstract: The aluminum matrix composite (AMC) coating reinforced with TiB was prepared utilizing in situ synthesized technique by laser cladding. Microstructural characterization and dry sliding wear behavior of in situ TiB/Al metal matrix composite were studied by SEM, XRD, TEM and Pin-on-disc friction and wear tester. The phase structure of the composite coating consists of α-Al, TiB, Al3Ti and Al3Fe. It has been found that the shape of in situ synthesized TiB is mainly taken on micro-magnitude lump and nano-magnitude whisker. Owing to B27 structure of TiB, the TiB has an anisotropy axis of growth, which results in the TiB strip and whisker preferring grown along [010] direction. It is worth to notice that the novel microstructure inside of TiB is particle and strip Al5Fe2 phase and definite crystallographic relationship between the Al5Fe2 phase and TiB has been determined by selected area diffraction pattern. The wear tests results show that the composite coatings can only improve wear resistance at the lower applied load (below 26.7N), but at higher applied load (26.7–35.6N) the wear resistance behavior of the coating is worsened due to the fracture and pullout of reinforcement phase. [Copyright &y& Elsevier]