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Structure and Properties of NiCoCrAlTaY Coating on Ti62421s Alloy Surface

Author: JiangZeMin
Tutor: XiaChangQing
School: Central South University
Course: Materials Science and Engineering
Keywords: NiCoCrAlTaY coating Vacuum heat treatment thediffusion behavior interfacial reactions oxidation resistance
CLC: TG178
Type: Master's thesis
Year: 2013
Downloads: 8
Quote: 0
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Abstract


Ti62421s alloy easy to be corroded in high temperature, this article use the arc ion plating (AIP) to prepare NiCoCrAlTaY coating on Ti62421s alloy surface to protect substrate alloy at high temperature. We analyse the coating surface and interface of coating/substrate organization and antioxidant properties of the coatings through vacuum heat-treatment and oxidation experiment at different regime. The experiment results indicate that:1Deposited NiCoCrAlTaY coating is made up of γ-Cr2Ni3phase、 γ’-Al4Ni15Ta phase and small amount of intermetallic NiCoCr phase; after vacuum heat treatment at650℃for3h, the γ’-Al4Ni15Ta phase increased, γ-Cr2Ni3phase decreased; γ’-Ni3Al phase appeared after750℃for3h vacuum heat-treatment; γ’-Ni3Al phase disappeared after vacuum heat treatment at850℃for3hours and found α-Cr and AlCr2phase; when heat treatment temperature rise to950℃, coating become invalid.2In650to850℃vacuum heat treatment process, NiCoCrAlTaY coating/substrate interface reaction sequence is as follows:First is Ni3(Al,Ti) and Ti2(Ni,Co) compound layer, and finally the Ti(Ni,Co) layer formed between the compound layer of Ni3(Al,Ti) and Ti2(Ni,Co).3In a650to850℃vacuum heat treatment process, the coating and the substrate occured inter-diffusion, the diffusion mainly element is Ni, Co and Ti. Above850℃, Al、Cr and Ta elements occured inter-diffusion,but their diffusion rate is much lower than Ni、Co, which lead to the enrichment of Al and Cr in the surface of the coating.4NiCoCrAlTaY coating weight gain by oxidation below1000℃was approximate parabolic relationship, the oxidation rate was significantly lower than the oxidation rate of the Ti62421s substrate. The coating of the oxidized at800℃mainly formed Al2O3AlTaO4, Cr2O3and NiCr2O4、CoCr2O4phase and a small amount of TiO2in the surface。 Oxidation experiment at900℃NiCr2O4、CoCr2O4phase disappeared, while TiO2phase increased.5NiCoCrAlTaY coating oxidation experiment at700、800℃there was no significant change in the surface;900℃the coating surface to formed a dense Al2O3oxidation film and protect the substrate; a lot of TiO2begin to grow from surface after1000℃oxidation experiment, the protection effect of coating was significantly weakened.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metal corrosion protection,metal surface treatment > The corrosion of various metals and alloys,corrosion and surface treatment
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