Hardness Of Composite Coatings Research Articles

Electrodeposited nickel–graphene nanocomposite coating: influence of graphene nanoplatelet size on wear and corrosion resistance

In this paper, we broaden our previous work, which investigated the influence of graphene nanoplatelets (GNPs) size on microstructure and hardness of composite coatings, to determine the effect of GNP size on wear-resistance and anti-corrosion property of GNP-reinforced nickel coating (Ni/GNPs). The experimental results indicated that the small GNP material size could enhance the wear resistance for nickel composite coating with the wear rate of 13.2 × 10–4 mm3/Nm, the wear depth of 17.69 µm. Meanwhile, the anti-corrosion property is enhanced significantly, this is shown via the low corrosion current density (Icorr value of 1.16 × 10–7 A/cm2) and the high corrosion potential (Ecorr value of − 0.1661 V). In addition, the mass lost in salt fog testing is low with the weight of 12.3 mg, which decreased down to ~ 55.27% compared to pristine Ni coating. These results are attributed to the uniform distribution of the small GNP size inside Ni matrix as well as the grain refinement effect of composite coating when using the small GNP size.

Effect of MoS2 content on microstructure and properties of supersonic plasma sprayed Fe-based composite coatings

In this paper, the high chromium Fe-based composite coatings with different mass fractions of MoS2 powders were prepared by supersonic plasma spraying technology. The influence of MoS2 addition on the microstructure, phase composition, hardness, coating-substrate bonding strength, and friction & wear properties was studied. The results show that the interface between the deposited coatings and the substrates exhibited no obvious detachment, and the porosity was reduced with the addition of MoS2. However, the hardness of composite coatings and bonding strength between coatings and substrates were decreased with the increase of MoS2 content. Attributed to the fact the Cr element in Fe-based powder played a role of stabilizing the ferrite phase and deoxygenation, no oxide and phase transformation of α-(Fe, Cr) were detected. The XRD results also revealed that partial decomposition of MoS2 occurred during the spraying process, leading to the formation of Mo. The worn surface morphology analysis showed that the wear mechanism of the Fe-based coating without MoS2 was mainly oxidative wear. Through the evolution of wear mechanism of three composite coatings, it is found that with the increase of MoS2 content, the phenomenon of abrasive & fatigue wear was intensified, owing to the reason that the bonding between Fe-based matrix material and MoS2 in the coating was poor. Therefore, the content of MoS2 should be rationally controlled in order to improve the friction & wear properties.

Effect of Graphene Carbon Nitride on Ultraviolet-Curing Coatings.

Graphene carbon nitride (g-C3N4) was successfully prepared by semi-closed pyrolysis and then incorporated into the ultraviolet (UV)-curing system to synthesize different specimens of g-C3N4-hybridized UV-curing (g-C3N4/UV) coatings. The apparent appearance and dispersity g-C3N4 were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The influence of the curing speed and mechanical properties was also tested. The dispersion level of g-C3N4 can be kept less than 1 μm by mechanical mixing. The pencil hardness of composite coatings could be 6H while the adhesion based on glass could be 1 level. The degree of curing of the coating could be obviously improved by the addition of g-C3N4, leading to a 7 percent increase of the gel content. Additionally, the decomposition of hard segments of polyurethane acrylate could be avoided by the use of g-C3N4 resulting in an increasing stability to heat. We found the gel content in an aerobic environment was lower than that in an anaerobic environment. On this basis, the function and mechanism of g-C3N4 was investigated in detail and methods to eliminate the O2 were proposed.

Plasma-Sprayed Ti6Al4V Alloy Composite Coatings Reinforced with In Situ Formed TiB-TiN

Plasma spraying was used to deposit premixed Ti6Al4V + 15 wt.% BN powder on titanium substrate to fabricate Ti6Al4V matrix composite coatings reinforced with in situ synthesized TiB-TiN. The formation of in situ TiB-TiN reinforcements increased with plasma power. The in situ reaction appears to be complete under present experimental conditions but with considerable oxidation of Ti in the composite coatings. The hardness of composite coatings was 7 times higher (855HV), and the in vitro wear rate (2.4 × 10−5 mm3/N m) was one order of magnitude less than that of titanium substrate. However, the microstructural non-uniformity decreased the corrosion resistance of these composite coatings in Hank’s balanced salt solution.

Development of Al356–Al2O3 Nanocomposite Coatings by High Velocity Oxy-fuel Technique

In this research, development of Al356–Al2O3 nanocomposite coatings has been investigated. Al356–Al2O3 composite powders were prepared by mechanical milling of Al356 powder and 5 vol.% micro and nanoscaled alumina particles. The milled powders were used as feedstock to deposit composite coatings on A356–T6 aluminum alloy substrate using high velocity oxy-fuel (HVOF) process. X-ray diffractometry, optical and scanning electron microscopy, microhardness and wear tests were used to characterize the composite powders and coatings. The hardness of composite coatings containing micro and nanosized Al2O3 were 114.1 ± 5.9 HV and 138.4 ± 6.9 HV, respectively which were higher than those for substrate (79.2 ± 1.1 HV). Nano and microcomposite coatings revealed low friction coefficients and wear rates, which were significantly lower than those obtained for Al356–T6 substrate. Addition of 5 vol.% micro and nanoscaled alumina particles improved the wear resistance by an average of 85% and 91%, respectively. This is mainly caused by the presence of Al2O3 in matrix and nanocrystalline structure of matrix. Scanning electron microscopy tests revealed different wear mechanisms on the surface of the wear test specimens.

Research on Crafts of Ni-P-SiC Electroless Composite Plating on Surface Performances of the Mould

Experiments of Ni-P-SiC chemical composite plating were carried out, and then the crafts and performances of Ni-P-SiC chemical composite plating were investigated. Based on the previous researches of the chemical composite plating, different amount of SiC particles and different conditions of technologies were selected. After experiments, the distribution surface particles, the metallographic structure and hardness of composite coatings were characterized by using a XJZ-6A type metalloscope and a HVS1000 type micro-hardometer, respectively. The results show that the composite coatings have bright surface appearance. Besides having a higher hardness, composite coatings combine well with the matrix and the deposition rate is quick. In the factors which influenced the properties of the composite coatings, the amount of SiC particles and plating time are analyzed.

Effect of surfactant on the co-electrodeposition of the nano-sized ceria particle in the nickel matrix

Abstract The nickel–ceria (Ni–CeO2) nanocomposite coatings have been pulse electrodeposited from a Watts-type electrolyte containing nano-sized CeO2 particles produced by high-energy ball milling technique (HEBM). Sodium Lauryl Sulphate (SLS) has been added in the electrolyte as a cationic surfactant. The effects of the surfactant on the zeta potential, co-deposition and distribution of ceria particles in the nickel matrix and hardness of composite coatings have been investigated. Experimental results show that the addition of SLS up to 0.10 g/l increases the amount of co-deposited ceria particles in the nickel matrix and microhardness of the nanocomposite. However, when the amount of SLS in the electrolyte is more than 0.1 g/l, there is a tendency to form agglomerates of ceria particles in the nickel matrix resulting no further increase in hardness of the Ni–CeO2 nanocomposite coatings.

The effect of SiC particles added in electroless Ni–P plating solution on the properties of composite coatings

To verify the relationship between the properties of composite coatings prepared on Q235 steel and the SiC content of electroless Ni–P–SiC composite coatings, systematic experiments with varied SiC contents and surfactants have been conducted. The experimental results indicated the approximate linear relation between the SiC content and the hardness of composite coatings. With the increasing of SiC content, wear resistance increases correspondingly. In particular, the effect of SiC content on the corrosion resistance of Ni–P–SiC composite coatings immersed in different corrosive solutions (i.e. 5% H 2SO 4, 20% NaOH and 3.5% NaCl) is explored, followed by a comparative analysis of the corrosion resistance between Ni–P and Ni–P–SiC coatings. Corrosion test indicates that NaOH solution makes no differences in the corrosion resistance between Ni–P coatings and electroless Ni–P–SiC composite coatings, both being uncorroded. Exposed to NaCl solution, the corrosion resistance of electroless Ni–P–SiC composite coatings decreases gradually with the increasing of SiC content in coatings. In H 2SO 4 solution, the corrosion resistance of coatings increases initially and decreases afterwards with the sustained increasing of SiC content in coatings, and the optimized corrosion resistance is obtained at a SiC content of 9.41 wt.%. Finally, a competent electroless Ni–P–SiC composite plating process producing a high wear resistance and sound corrosion resistance of the coatings is obtained.