Effects of plasma surface Ta alloying on the tribology behavior of γ-TiAl

To improve the wear resistance of ?-TiAl alloy, Ta alloy layer was prepared on surface by double glow plasma surface alloying technique. The tribology behavior of Ta alloy layer against Si3N4 at 25?, 350? and 500? were comparatively studied. The results showed that Ta alloy layer comprised a deposition layer and a diffusion layer. The deposition layer played a role in protection as a soft film. With the increase of temperature, the wear mechanism of ?-TiAl changed from abrasive wear to coexistence of abrasive wear and oxidation wear. Ta alloy layer?s wear mechanism changed from adhesive wear to coexistence of adhesive wear and oxidation wear. Surface Ta alloying process significantly reduced the wear volume, the specific wear rate and the friction coefficient of ?-TiAl and improved the wear resistance properties of ?-TiAl.

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.

Isothermal Oxidation Behavior of Zr-Y Coating on γ-TiAl by Double Glow Plasma Surface Metal Alloying Technique

Oxidation resistance of Zr-Y coating on γ-TiAl alloy prepared by a double-glow plasma surface alloying technique was investigated in static air at 750 °C, 800 °C and 850 °C for 100 h. A pure Zr coating was also prepared for comparison. Addition of Y improved high-temperature oxidation resistance of the alloying coating because of its refining effect and inhibition of cationic diffusion. Oxidation kinetic curves indicated that the high-temperature oxidation resistance of the Zr-Y coating was about eight times higher than that of the bare substrate and about 3 times higher than that of pure Zr coating.

FRICTION AND WEAR BEHAVIORS OF Ti6Al4V ALLOY TREATED BY PLASMA Ni ALLOYING

The Ni modified layer was prepared on surface of the Ti6Al4V substrate by plasma surface alloying technique (PSAT). The cross-section micro structure, phase structure and microhardness of Ni modified layer were studied. The friction and wear behavior of the Ni modified layer and the Ti6Al4V substrate were analysed. The effects of displacement amplitude, frequency and fretting time on friction coefficient of the Ni modified layer were investigated. The results indicated that the wear rate was lower compared with that of the Ti6Al4V substrate. Friction coefficient of the Ni modified layer increased with the increase of frequency. But it was insensitive to the change of wear time and the displacement amplitude. The wear mechanism of the Ti6Al4V was adhesion and abrasion wear mechanism while the Ni modified layer showed slightly abrasion wear.

Oxidation Behavior of TiAl-Based Alloy Modified by Double-Glow Plasma Surface Alloying with Cr–Mo

A Cr–Mo alloyed layer was prepared on a TiAl-based alloy using plasma surface alloying technique. The isothermal oxidation kinetics of the untreated and treated samples was examined at 850 °C. The microstructure and phase composition of the alloyed layer were analyzed by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray powder diffraction (XRD). The morphology and constituent of the oxide scales were also analyzed. The results indicated that the oxidation resistance of TiAl was improved significantly after the alloying treatment. The oxide scale eventually became a mixture of Al2O3, Cr2O3 and TiO2. The oxide scale was dense and integrated throughout the oxidation process. The improvement was mainly owing to the enhancing of scale adhesion and the preferential oxidation of aluminum brought by the alloying effect for TiAl-based alloy.