Performance Enhancement in Borocarburized Low-Carbon Steel by Double Glow Plasma Surface Alloying

In this paper, the performance of low-carbon steel is enhanced after introducing a borocarburized diffusion layer via double glow plasma surface alloying technology. Due to the boron-carbon gradient structure of low-carbon steel, the protective coating exhibits an excellent wear and corrosion resistance. Interestingly, the borocarburized layer consists of a 64 μm carburized layer and a 27 μm boride layer, which plays an effective role in enhancing the microhardness of borocarburized low-carbon steel, exhibiting a 1440 Vickers hardness increase in the surface microhardness of low-carbon steel. The potentiodynamic polarization measurement and impedance measurement results indicate that the boride protective film can effectively prevent aggressive chloride ions from invading the substrate, which indicates an excellent property of corrosion resistance. This systematic study paves a promising way for the future application of hard coatings in severe environments.

TRIBOLOGICAL AND CORROSION BEHAVIOR OF SiC/TaXC BILAYER COATINGS PREPARED ON STAINLESS STEEL SURFACE BY DOUBLE GLOW PLASMA SURFACE ALLOYING TECHNIQUE

In this work, SiC/TaxC bilayer coatings were prepared on stainless steel surface by double glow plasma surface alloying technique to improve the wear and corrosion resistance of the substrate. The effect of reaction temperature during the growth of SiC on the microstructure and property of the coating was investigated. The results showed that the surface topography of the coating could be regulated by the reaction temperature during the growth of SiC. Interactional flower-shaped rings, reticulate patterns, nanoparticles and microparticles were observed on the samples prepared at 750∘C, 800∘C, 850∘C and 900∘C, respectively. Tribological performance tests showed that the friction coefficient and specific wear rate of all the coated specimens were significantly decreased than the uncoated ones, indicating that the wear resistance of stainless steel was improved by the SiC/TaxC coating. The construction of the bilayer coating enhanced the corrosion resistance of stainless steel in terms of electrochemical tests. With an increase of the reaction temperature, the wear and corrosion resistance increased at first and then gradually decreased. SiC/TaxC coating prepared at 800∘C exhibited the best overall performance.

Preparation, Microstructure, Mechanical Properties and Biocompatibility of Ta-Coated 3Y-TZP Ceramic Deposited by a Plasma Surface Alloying Technique

A Ta coating has been successfully fabricated on the surface of zirconia polycrystals ceramic (3 mol% yttria, 3Y-TZP) by a plasma surface alloying technique. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results showed that a α-Ta coating with a continuous and compact surface morphology which consisted of a deposited layer with a thickness of 390 nm and a diffusion layer with a thickness of 200 nm covered the 3Y-TZP. Due to the effect of inhabitation the t→m transformation by the deposited Ta coating, the biaxial flexural strength caused by the phase transformation during hydrothermal aging is reduced e.g., p < 0.05 after 20 h and/or 100 h. In addition, the Ta coating shows non-cytotoxicity and improved proliferation ability of osteoblasts.

Effect of Heating Treatment on the Microstructure and Properties of Cr–Mo Duplex-Alloyed Coating Prepared by Double Glow Plasma Surface Alloying

In this study, Cr–Mo duplex-alloyed coating was prepared on carbon steel by double glow plasma surface alloying (DGPSA). The effect of annealing and quenching and tempering (Q&T) treatments on the microstructure and performance of the coating was investigated by X-ray diffraction (XRD), energy dispersive spectrometry (EDS), backscattering electron imaging (BSEI) and electron backscattering diffraction (EBSD) techniques. The results show that a gradient structured coating composed of an Fe–Cr–Mo solid solution (Fe–Cr–Mo SS) layer and an alloyed pearlite layer was obtained on the steel surface. The affected layer was adjacent to the coating. After annealing or Q&T, more carbides precipitated in the Fe–Cr–Mo SS layer and alloyed pearlite layer. Most of the C atoms in the subsurface were dragged into the coating to form carbides in the Fe–Cr–Mo SS and alloyed pearlite layers of the coating, transforming the affected layers into a carbon-poor zone. Annealing and Q&T hardly modified the thickness of the coating, but greatly changed the hardness and corrosion resistance of the coating. The Q&T treated samples had higher hardness and better corrosion resistance than the as-DGPSA treated and the annealed samples.