Influence of laser re-melting and vacuum heat treatment on plasma-sprayed FeCoCrNiAl alloy coatings

FeCoCrNiAl high entropy alloy coatings were prepared by supersonic air-plasma spraying.The coatings were post-treated by vacuum heat treatment at 600 and 900°C,and laser re-melting with 300 W,respectively,to study the influence of different treatments on the structure and properties of the coatings.The phase constitution,microstructure and microhardness of the coatings after treatments were investigated using X-ray diffraction,scanning electron microscopy and energy dispersive spectrometry.Results showed that the as-sprayed coatings consisted of pure metal and Fe-Cr.The AlNi;phase was obtained after the vacuum heat treatment process.A body-centered cubic structure with less AlNi;could be found in the coating after the laser re-melting process.The average hardness values of the as-sprayed coating and the coatings with two different temperature vacuum heat treatments and with laser re-melting were 177,227,266 and 682 HV,respectively.This suggests that the vacuum heat treatment promoted the alloying process of the coatings,and contributed to the enhancement of the coating wear resistance.The laser re-melted coating showed the best wear resistance.

Electrodeposition of nanostructured Ti/(Ru+Ti+Ce)O_2 coatings

A nanostructured ternary coating of Ti/（Ru ＋ Ti ＋ Ce）O2 was prepared by the conventional electrodeposition on the titanium substrate as the cathode with different numbers of coating layers. The main objective of this work was to study nanostructured coatings of ceramic materials. For this purpose, the amount of precursor materials in the electrolyte was a variable parameter. Furthermore, the salt of TiCl4/RuCl3·xH2 O/Ce（NO3）3·6 H2 O with different amounts, hydrogen peroxide, methanol, and distilled water were used as an aqueousunaqueous bath. In addition, the coated samples were put to heat at 300, 450, 650, and 850℃ in an electric furnace for1 h. The crystalline phase of the coating was characterized by X-ray diffraction（XRD）. The chemical composition and microstructure of the coating were studied using energydispersive spectroscopy（EDS） and scanning electron microscopy analysis（SEM）. Moreover, the electrochemical measurement of Ti/（Ru ＋ Ti ＋ Ce）O2 coatings was carried out. Results show that with the increase in the number of coating layers, the quality of morphology is improved.Then, the best quality of coatings is obtained at six layers on the titanium substrate with electrolyte including TiO2/RuO2/CeO2 with the molar ratio of 70：5：25 after heat treatment at 450 ℃ for 1 h. Besides,with the increase in Ce02 content from 5 wt% to 25 wt% and the number of coating layers, higher thickness of about（20.0±0.1） μm and minimum over potential for chlorine evolution were obtained.

Deposition of Phase-pure Cr2AlC Coating by DC Magnetron Sputtering and Post Annealing Using Cr-Al-C Targets with Controlled Elemental Composition but Different Phase Compositions

Polycrystalline Cr2AlC coatings were prepared on M38G superalloy using a two-step method consisting of magnetron sputtering from Cr-Al-C composite targets at room temperature and subsequent annealing at 620 ℃. Particularly, various targets synthesized by hot pressing mixture of Cr, Al, and C powders at 650-1000 ℃ were used. It was found that regardless of the phase compositions and density of the com- posite targets, when the molar ratio of Cr：Al：C in the starting materials was 2：1：1, phase-pure crystalline Cr2AlC coatings were prepared by magnetron sputtering and post crystallization. The Cr2AIC coatings were dense and crack-free and had a duplex structure. The adhesion strength of the coating deposited on M38G superalloy from the 800 ℃ hot-pressed target and then annealed at 620 ℃ for 20 h in Ar exceeded 82 ± 6 MPa, while its hardness was 12 ± 3 GPa.