Key Engineering Materials Vols. 336-338

Abstract: Ni/Al-Al2O3 gradient ceramic coating was prepared on Q235 steel by plasma spraying. Microstructure and corrosion behavior in boiling 5%HCl solution of the samples sprayed with this coating were investigated. The results showed that thickness of Al2O3 ceramic coating was increased greatly and almost no connected pores formed in the gradient coating due to the existent of Ni/Al-Al2O3 transition interlayer coatings. The corrosion resistance of Q235 steel with Ni/Al-Al2O3 gradient composite ceramic coating in boiling 5%HCl solution was greatly improved.

Abstract: X-ray diffraction (XRD) method to measure the residual stress existing in the metal substrate surface layer was introduced and the sol-gel ZrO2-CeO2 thin film was successfully prepared on SUS304 stainless steel substrate by dip-coating process. The macro residual stress existing in metal substrate was analyzed by XRD. It turns out that the compressive stress existing in the metal substrate surface layer increases with the increase of heat-treated temperature. Based on the above study, colored stainless steels of high quality were prepared by sol-gel process.

Abstract: The influence of heat-treated temperature and the CeO2 content on the chemical composition and the valence state of elements on surface of ZrO2-CeO2 thin films deposited on metal substrates has been studied by X-ray photoelectron spectroscopy. Results show that: elements of Fe, Cr, Zr, Ce exist in the form of their respective stable state, such as Fe2O3, (Fe0.6Cr0.4)O3, ZrO2, CeO2, when heat treated at 600°C and 700°C for 2h respectively; with the increase of heat-treated temperature, the area of oxygen with O1s peak corresponding to value of bonding energy 529.28ev increases, but the area of oxygen with O1s peak corresponding to value of bonding energy 531.7ev decreases.

Abstract: Amorphous titania coatings on copper particles were prepared by using tetrabutyl titanate to improve the anticorrosion property. The coated particles were characterized by SEM, EPMA and XRD. Experimental results showed that the resistance to oxidation of the coated copper particles depended on the stability and content of the sol. The proper pH value for the sol was about 4, and the ratio of tetrabutyl titanate and water was 1 to 2. The transmissivity of the etching solution of coated copper particles in 5% of H2SO4 was more than 80%, showing that the TiO2 coatings on copper particles exhibit an excellent corrosion resistance.

Abstract: Three mole percent Y2O3 doped tetragonal polycrystals (TZP) and stainless steel functionally graded materials (FGMs) were fabricated by slip casting. The optimal conditions for control of interfacial cracks by adjusting shrinkage of each component and temperature gradient were investigated. Experimental results showed that sintering shrinkage mismatch of adjacent intermediate interlayer could cause interface cracks, as well as speedy temperature dropping rate in the cooling process. Based on suitable adjusting of sintering shrinkage and controlling of cooling rate, a satisfying interfacial microstructure without apparent cracks for FGM of 3Y-TZP/SUS with three intermediate layers was obtained.

Abstract: A method of the aluminizing treatment on the surface of Cu-Al-Y alloy with addition of rare earth compound CeCl3 in 1173K was carried out. The followed internal oxidation of the aluminized Cu-Al-Y alloy was also carried out in the commercial nitrogen gas medium to generate Al2O3 dispersed hardening copper matrix composites. The hardness distribution in aluminized layer and microstructure were studied. Results show that the addition of rare earth oxide CeCl3 has great accelerating effect on the aluminizing, the aluminized layer deeper and uniform than that not add CeCl3 at the same condition. It is possible to generate Al2O3 particles dispersed hardening layer depth reached about 200μm in the surface of specimens with aluminizing and internal oxidation technique.