Abstract
Alumina oxide coatings are widely used in many industrial applications to improve corrosion protection, wear and erosion resistances, and thermal insulation of metallic surfaces. The paper presents study of the microstructure, mechanical, and wear properties of HVOF (high velocity oxy-fuel process) sprayed of Al2O3-15 wt.% TiO2 coating with the NiAl interlayer on the surface of Al-Si alloy castings. The microstructure of Al2O3-15 wt.% TiO2/NiAl coating was characterized by light microscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS). The analysis of the microstructure showed the formation of coating with low porosity, compact structure, good adhesion to the substrate with typical lamellar structure composed of a solid phase consisting of compounds included in the coating material and their phase variations. For analysis of the adhesion of coatings to the substrate, the scratch test was applied. An assessment of the erosive wear resistance of coatings was also carried out, confirming the significant impact of the interlayer as well as the microstructure and phase composition of the oxide coating on the wear resistance of the tested coating system. Moreover, the results were discussed in relation to the bending strength test, including cracks and delamination in the system of the Al2O3-15 wt.% TiO2/NiAl/Al-Si alloy as microhardness and erosion resistance of the coating. It was found that the introduction of the NiAl metallic interlayer significantly increased resistance to cracking and wear behavior in the studied system.
Highlights
Aluminum oxide-based compositions are an important group of ceramic coating materials with many advanced properties such as heat resistance, corrosion resistance, wear resistance, chemical resistance, and excellent mechanical properties such as hardness, fracture toughness, and strength
2 ceramic coating applied by the HVOF method, after initial application to the interlayer surface NiAl by the same method, has a typical lamellar structure, without cracks and
Al2O3-15 wt.% TiO2 ceramic coating applied by the HVOF method, after initial application to with the good adhesion to the substrate
Summary
Aluminum oxide-based compositions are an important group of ceramic coating materials with many advanced properties such as heat resistance, corrosion resistance, wear resistance, chemical resistance, and excellent mechanical properties such as hardness, fracture toughness, and strength. Sprayed coatings based on Al2 O3 have been extensively tested over the last decade, especially those containing various TiO2 additives [1,2,3,4,5]. The machinability, wear resistance, or conductivity of the coatings can be adjusted by changing the TiO2 content. Coatings, which are constructed from a combination of these oxides, have better properties than both oxides used separately, which gives a wider range of application of these coatings. The best wear resistance and toughness is achieved with coatings with the addition of 13 wt.% of TiO2 [6].
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