Jining He

An investigation of the corrosion behavior of Al2O3-based ceramic composite coatings in dilute HCl solution

Abstract In this paper, the corrosion behavior of Al 2 O 3 –SiO 2 , Al 2 O 3 –TiO 2 and Al 2 O 3 –SiO 2 –TiO 2 ceramic composite coatings in boiling 1 N HCl solution is investigated. It is shown that the addition of 3% SiO 2 to the base spraying powder of Al 2 O 3 increases porosity in the coatings and causes deterioration in their corrosion resistance. Adding 13% TiO 2 to Al 2 O 3 improves the anti-corrosion property of the ceramic coating due to a reduction in porosity. The connected porosity in the Al 2 O 3 -based ceramic composite coatings rises with the open porosity and is independent of the density of the coating.

Studies on composite coatings prepared by plasma spraying Fe2O3–Al self-reaction composite powders

Abstract Fe 2 O 3 –Al composite powders were prepared using ferric oxide agent powders, aluminum powders and polyvinyl alcohol. Self-reaction composite coatings containing ceramic and metal multi-phases were fabricated by plasma spraying Fe 2 O 3 –Al composite powders. This technology successfully combines self-propagating high-temperature synthesis with plasma spraying. The morphology of the composite powders was examined by scanning electron microscope (SEM). The chemical composition, microstructure, Vickers hardness, density, porosity and wear resistance of the composite coating were studied. The wear resistance of the ceramic and metal multi-phase composite coating was significantly improved under heavy load.

The corrosion behavior of plasma-sprayed Ni/Al–Al2O3 and Ni/Al–Al2O3+13 wt.% TiO2 graded ceramic coatings in 5%HCl solution

Abstract The corrosion behavior of plasma-sprayed Ni/Al–Al 2 O 3 and Ni/Al–Al 2 O 3 +13 wt.% TiO 2 graded ceramic coatings in 5%HCl solution was investigated. It was shown that the corrosion resistance of a Ni/Al–Al 2 O 3 graded coating was 130 times that of a single Al 2 O 3 coating. The corrosion resistance of Ni/Al–Al 2 O 3 +13%TiO 2 graded coatings was increased by 39.2% compared to a Ni/Al–Al 2 O 3 graded coating with the same compositional gradient. The improvement in corrosion resistance of graded ceramic coatings mainly resulted from the change of corrosion behavior due to the change in structure of the coating. The bond layer alloy particles in the transition layers were distributed isolated in the ceramic matrix. Thus, the connected pores in the working layer were actually pseudo-connected pores. As a result, the electrochemical corrosion between the bond layer and the matrix was restrained. In addition, the pseudo-connected porosity in graded coatings lay on not only the open porosity but also the structure of the graded coating.

Dry sliding wear behavior of ceramic-metal composite coatings prepared by plasma spraying of self-reacting powders

Ceramic-metal composite (CMC) coatings were deposited on the surface of Fe-0.14–0.22 wt.% C steel by plasma spraying of self-reacting Fe2O3−Al composite powders. The dry sliding friction and wear character of the CMC coatings are investigated in this paper. The wear resistance of the CMC coatings was significantly better than that of Al2O3 coatings under the same sliding wear conditions. The tough metal, which is dispersed in the ceramic matrix, obviously improved the toughness of the CMC coatings. Wear mechanisms of the CMC coatings were identified as a combination of abrasive and adhesive wear.

Corrosion behavior in boiling dilute HCI solution of different ceramic coatings fabricated by plasma spraying

An Al2O3 ceramic coating (A), a 13 wt.% TiO2-Al2O3 (13TA) composite ceramic coating, and a Ni-Al-13wt.%TiO2-Al2O3 (NA-13TA) gradient composite ceramic coating were prepared on Q235 steel by plasma spraying. The corrosion behavior of samples sprayed with these coatings in a boiling 5% HCl solution was investigated. It was shown that an A ceramic coating and a 13TA composite ceramic coating were destroyed after immersion for 17 and 23 h, respectively. The NA-13TA gradient composite ceramic coating was still sound after 14 days of immersion. The corrosion resistance of samples with the NA-13TA gradient composite ceramic coating was sharply improved due to the decreased amount of connected pores in the coating. The corrosion of the sample sprayed with the gradient ceramic coating included the partial corrosion of the surface ceramic coating and the interlayer coatings. The corrosion weight loss depended on the degree of open porosity.

TITANIUM CARBONITRIDE COATINGS PREPARED BY REACTIVE PLASMA SPRAYING Ti POWDERS

Titanium Carbonitride (TiCN), a new high hardness and wear-resistant material, has been applied widely in many fields. TiCN coating was first fabricated using reactive plasma spraying (RPS) technology in the reactive chamber that was filled with nitrogen and acetylene (N2 and C2H2) in this study. The microstructure and the phase composition of the coatings were analyzed by SEM and XRD. More chemical information of surface was analyzed by XPS. The Vickers microhardness of TiCN coating is 1659.11 HV100g, and the cross-section of the coating shows a conspicuous phenomenon of indentation size effect.

Microstructure and Mechanical Properties of Aluminum Clad Steel Plates by Cold Rolling and Annealing Heat Treatment

Aluminum clad steel plate has been successfully fabricated by cold rolling and annealing heat treatment. The thicknesses of total clad plate and aluminum cladding layer were about 1.5 mm and 50–70 μm, respectively. The grain morphology, mechanical properties revealed a slight anisotropy. Herein, the grains were severe elongated along the cold rolling direction. The clad plates exhibited a superior tensile elongation and slight interfacial delamination, and highest value of multiple bending fracture times was located at the clad plate along the angle of 45°. Moreover, the perfect interfacial brazing bonding presented at the base clad plate and fins, which can be used in the power station.