Kong Dejun

Effects of laser remelting on surface-interface morphologies, bonding modes and corrosion performances of arc-sprayed Al coating

Purpose The purpose of this paper is to provide an experimental basis for studying the effects of laser remelting on the surface modification of arc-sprayed Al coating. Design/methodology/approach A layer of arc-sprayed Al coating on S355 steel was remelted with a CO2 laser, and the surface-interface morphologies, compositions of chemical elements and phases of Al coating were analyzed with scanning electron microscopy, energy disperse spectroscopy and X-ray diffraction, respectively. The effects of laser remelting on compositions of chemical elements and bonding performance of Al coatings were discussed. Findings The result shows that there are some pores existing on the Al coating surface after arc spraying, and the combination mode of coating interface is primarily composed of mechanical bonding. The pores on the Al coating reduce after laser remelting, which improves the compact performance, and the mechanical binding mode by arc spraying is changed into metallurgical bonding. The Fe and Al atoms at the coating interface are distributed with gradient, and the stratified enrichment is evident, which improves binding performance of the Al coating. The Al coating exhibits general corrosion before laser remelting and local corrosion after laser remelting, which improves the corrosion resistance of Al coating. Originality/value The arc-sprayed Al coating is remelted by CO2 laser, improving its microstructures and bonding mode with the substrate.

SURFACE CHARACTERISTICS AND WEAR RESISTANCE OF AlCrTiSiN COATINGS AT HIGH TEMPERATURES

AlCrTiSiN coatings were deposited on YT14 cemented carbide using cathodic arc ion plating (CAIP) method. The surface and cross-section morphologies, chemical composition, phases, surface roughness, and binding energies of chemical elements of obtained coatings were analyzed using a field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffractometer (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), respectively, and its mechanical properties were characterized using a scratch tester and nanoindentation tester. The friction-wear behaviors of AlCrTiSiN coatings at 700∘C, 800∘C and 900∘C were investigated using a high temperature wear test, the distributions of chemical elements on the worn tracks were analyzed using a plane scan analysis of EDS, and the high temperature wear mechanisms were also discussed. The results show that the chemical elements are uniformly distributed on the AlCrTiSiN coating with the surface roughness of 105nm, which is composed of faced centered cubic (FCC)–(Cr, Al)N, body-centered cubic (HCP)–AlN and Si3N4 amorphous phases. The interfacial bonding strength, microhardness and elastic modulus of AlCrTiSiN coating is 26.15N, 25.789GPa, and 251.364GPa, respectively. The average coefficient of friction (COF) of AlCrTiSiN coatings at 600∘C, 700∘C and 800∘C is 1.06, 0.73, and 0.97, respectively, of which friction performance is the best at 700∘C. The wear mechanism of AlCrTiSiN coating at 600∘C, 700∘C and 800∘C is adhesive wear + fatigue wear, abrasive wear + oxidation reaction, and adhesive wear + fatigue wear, respectively.

Microstructures and High-Temperature Friction–Wear Performance of Laser-Remelted WC-12Co Coatings by HVOF

ABSTRACT A WC-12Co coating prepared by high-velocity oxygen fuel (HVOF) was remelted with a CO2 laser, and the surface–interface morphologies, plane energy spectrum, and phases of the coating were analyzed by means of field emission scanning electron microscopy (FESEM), energy-dispersive spectrometry (EDS), and X-ray diffraction (XRD), respectively. The friction and wear behaviors of the WC-12Co coating were investigated at high temperature with a wear test, and the morphologies and the changes in chemical elements on the wear scar after the wear test were analyzed with SEM and EDS, respectively. In addition, the influence of high temperature on the coefficient of friction (COF) and wear performance is discussed. The results show that the substrate is closely bonded with the substrate after laser remelting (LR), which includes mechanical bonding accompanied by metallurgical bonding. The average coefficient of friction (COF) at 600, 700, and 800°C is 0.6832, 0.3957, and 0.1922, respectively. The wear mechanisms of WC-12Co coating at 600 and 700°C are adhesive wear, abrasive wear, and oxidative wear, respectively, and the wear mechanism of the coating at 800°C is serious oxidative wear.

Surface–Interface Microstructures and Friction-Wear Performances of Thermal Sprayed FeCrBSi Coatings Obtained by High-Velocity Oxygen Fuel Process

A layer of FeCrBSi coating was prepared on H13 hot work steel using a high-velocity oxygen fuel spraying (HVOF). The morphologies and distribution of chemical elements and phases in the obtained coatings were analyzed using a field emission scanning electron microscopy (FMSEM), energy dispersive spectrometry (EDS), and X-ray diffraction (XRD), respectively. The friction-wear performance of FeCrBSi coating was examined using a wear test, and the wear mechanism was also discussed. The results show that the coating is primarily composed of Fe, Cr, B, and Si elements, which are uniformly distributed in the coating, enriched in the coating, and poor in the substrate at the coating interface. Among them, the Fe content decreases gradually in the substrate–coating direction, the Fe content of the coating is 40% lower than that of the substrate. The Cr, B, and Si contents in the coating are higher than those in the substrate, which form compounds and diffusion at the interface; as a result, the coating is combined with the substrate in the form of metallurgical bonding. The coating has a good friction reduction and wear resistance, the average COF (coefficient of friction) is 0.2126, the wear rate is 1.5 ∙ 10–6 mm3/sec ∙ N, and the wear mechanism consists abrasive wear and spalling.