Search

In this study, C 3 N 4 coating was successfully fabricated on AISI 304 stainless steel by electrochemical deposition method using N-N dimethylformamide (DMF) and KCl as the electrolyte. The influences of DMF concentration on the microstructure, hardness, and wear resistance of the coatings were investigated by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Vickers hardness tester, and pin-on-disk wear tester. The results indicate that a continue C 3 N 4 coating layer can be formed on the steel surface. Compared to the untreated sample, the surface hardness and wear resistance of the stainless steel can be improved apparently after depositing of C 3 N 4 coating. The hardness and wear resistance of the coatings increase firstly and then decrease with increase of DMF concentration. The coatings fabricated with 50 % DMF possess the highest hardness of 1329 HV 0.05 and the lowest friction coefficient of 0.35 at 5 N. The main wear mechanisms are fatigue wear, abrasive wear, and oxidative wear. Deposition of C 3 N 4 coating conforms to the polarization-adsorption-electrochemical reaction mechanism in the present investigation conditions. [Display omitted] • C 3 N 4 coating can be successfully prepared by electrochemical deposition on AISI 304 stainless steel • C 3 N 4 coatings exhibit the high hardness and wear resistance • Deposition of C 3 N 4 coating conforms to the polarization–adsorption–electrochemical reaction mechanism [ABSTRACT FROM AUTHOR]

The structures of carbon-expanded α phase (α C) phase were modeled with nominal molecular formula of Fe 13-x Cr 3 Ni x C y (x = 0, 1, y = 0,1,2,3,4) based on body-centered cubic α-Fe and calculated by first-principles calculation using density functional theory (DFT). The results show that Fe 13 Cr 3 C y (y = 0,1,2,3,4) structures with less than 11.11 at% carbon (y = 2) can be easily formed and exist stable. The Young's moduli of stable Fe 13 Cr 3 , Fe 13 Cr 3 C, and Fe 13 Cr 3 C 2 are 227.08 GPa, 209.71 GPa and 189.19 GPa, respectively. The theoretical hardness of stable Fe 13 Cr 3 C y (y = 1, 2) are obviously improved and can be up to 8.26 GPa. As for Fe 12 Cr 3 NiC y (y = 0,1,2), Young' s moduli of Fe 12 Cr 3 Ni, Fe 12 Cr 3 NiC, and Fe 12 Cr 3 NiC 2 are 155.82 GPa, 258.24 GPa and 207.44 GPa, respectively. The hardness of Fe 12 Cr 3 NiC y (y = 1,2) can be as high as 17.88 GPa. Ni element can stabilize the structures of Fe 13 Cr 3 C y (y = 1,2) and improve their theoretical hardnesses. The toughness of Fe 13 Cr 3 C y (y = 1,2) structures are shown in ductility based on Pugh's ratio criterion, while the Fe 12 Cr 3 NiC y (y = 1,2) structures are shown in brittleness. Electronic structure calculation shown that there are mixture bonding of metal bonding, covalent bonding, and ionic bonding in Fe 13-x Cr 3 Ni x C y (x = 0,1, y = 1,2) structures, which should account for the high hardness of the structure for α C phase. • Optimization position of Cr atom in α-Fe with BCC structure was obtained. • Hardness of stable Fe 13-x Cr 3 Ni x C y (x = 0, 1, y = 1,2) can be as high as 17.88 GPa. • Effects of Ni element on mechanical properties of α C phase were given. • New covalent bonding and ionic bonding account for high hardness of the structure for α C phase. [ABSTRACT FROM AUTHOR]

[Display omitted] • Microstructures and properties of three coatings Ni-P, Ni-P-TiN and Ni-P-TiN-Re are studied. • Re addition can significantly increase the deposition rate of Ni-P-TiN. • Re addition leads to a remarkable increase in crystallization temperature of coating. • Re addition can further improve hardness and wear resistance of Ni-P-TiN coating. Three different types of coatings Ni-P, Ni-P-TiN and Ni-P-TiN-Re are successfully prepared on a copper substrate by electroless plating. The effects of TiN and TiN + Re addition on surface morphology, microstructure, phase composition, deposition rate, thermal stability and wear resistance are investigated. Results show that all coatings exhibit amorphous microstructures, and that Re addition can significantly increase the deposition rate based on the coating thickness. X-ray diffraction of the coating before and after annealing indicates that the addition of TiN nanoparticles to the Ni-P coating barely affects the microstructures and phase transformation behavior, while the addition of Re results in a remarkable increase in crystallization temperature. Regardless of whether it is annealed or not, the wear resistance of Ni-P coating can be significantly improved after the co-deposition of TiN or TiN + Re, and the synergy effect of Re and TiN can further enhance the improvement. These findings provide a pathway to efficiently produce Ni-P-nano TiN composite coatings with excellent performance and thus have great potential in large-scale industry applications. [ABSTRACT FROM AUTHOR]