Glow Plasma Surface Alloying Technology Research Articles

Isothermal oxidation behavior and microstructure of plasma surface Ta coating on γ-TiAl

The oxidation behavior of γ-TiAl with Ta surface coating fabricated by double glow plasma surface alloying technology was investigated by thermogravimetric method. Oxidation experiments were carried out at 750°C and 850°C in air for 100h. The modification layer was comprised of deposition layer and diffusion layer, which metallurgically adhered to the substrate. Tantalum element decreased with the case depth. The oxidation morphology was studied by a scanning electron microscope and X-ray diffraction. The results highlighted that in the oxidizing process of the oxidation, the phase containing Ta-richer may restrain diffusing outward of the element Al in the matrix. Ti diffused outward, and formed the TiO2 scales, while the middle layer was rich in Al, and formed the continuous Al2O3 scales after oxidation, which was effective to prevent further infiltration of oxygen atoms, and as a result the oxidation resistance increased immensely.

Microstructure and corrosion resistance of pure titanium surface modified by double-glow plasma surface alloying

In this paper, the TiO2 alloyed layer was successfully formed on pure titanium surface using the double glow plasma surface alloying technology. The microstructure and phase composition of the alloyed layer were analyzed by optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray powder diffraction (XRD). The micro-hardness of the alloyed layer was investigated by nano-indentation test. The surface roughness was decreased after the treatment. Measuring the anodic polarization curves in Tyrode’s solution, the corrosion rates of the untreated and treated samples were compared. The results indicated that the uniform dense TiO2 alloyed layer was obtained on the pure titanium surface. As compared with pure titanium, the free corrosion potential of TiO2 alloyed layer increased and the free corrosion current density decreased, which corresponded to a decreased corrosion rate. It led to the improvement of corrosion resistance of the pure titanium surface.

FRICTION AND WEAR PROPERTIES OF SURFACE PLASMA Cr-W ALLOYING LAYER OFγ-TiAl ALLOY

Cr-W alloying layer was prepared on the TiAl alloy by using the double glow plasma surface alloying technology (DGP). The hardness tests show that the surface micro-hardness of Cr-W alloying layer is greatly increased and the micro-hardness of diffusion layer is 648.8 HV0.1, increased two times more than the matrix. The scratch tests show that the bond between TiAl alloy and Cr-W alloying layer is very good and the layer at least can withstand 70 N vertical load. The friction and wear at room temperature tests show that the friction coefficientof Cr-W alloying layer is about 0.43, that of the matrix is 0.70. The wear scar is narrow, and the depth is small. The wear weight loss and wear rate relative to the matrix decrease greatly. The friction and wear at 500 tests show that the friction coefficient of Cr-W alloying layer is about 0.50, that of the body is 0.75. The wear weight loss and wear rate of Cr-W alloying layer are all less than the matrix.

P-09 laser ablation performance of double glow discharge sputter deposition Mo on titanium alloy surface

In order to improve the burn-resistant property of titanium (Ti) alloy, Ti-molybdenum (Mo) burn-resistant alloyed layer is coated onto the Ti6Al4V substrate with the double glow plasma surface alloying technology by permeating the Mo. The experiment is performed at a working temperature of 800 ˚C to keep the layer warm for 2.5 h under air pressure of 30 Pa. Mo and Ti6Al4V are used as the source electrode and cathode, respectively. The result of X-ray diffraction shows that the alloy phase of Ti and Mo is formed on the surface of Ti6Al4V substrate. The hardness of the alloyed layer on the surface is more than 800 HK. The friction result further indicates that wear rate can be reduced by three orders of magnitude. Laser ablation experiment is used to characterize the burn-resistant properties of the Ti alloy. The result indicates that the laser burn area of the treated Ti alloy is reduced to 1/12 of the untreated sample. Moreover, the burn-resistant properties improved greatly. Current experimental results clearly show that the laser ablation can be used to characterize the burn-resistant property of the material. OCIS codes: 160.0160, 140.3390, 240.6700, 120.0120. doi: 10.3788/COL201109.S10704.

Tribological Properties of Laser Surface Texturing and Molybdenizing Duplex-Treated Ni-Base Alloy

Laser surface texturing (LST) and surface molybdenizing duplex-treatment was performed on Ni-base alloy in order to improve its wear resistance at high temperature. Surface molybdenizing was performed on the laser surface textured Ni-base alloy by a double glow plasma surface alloying technology. The friction and wear properties of the duplex-treated, the single-treated, and the untreated alloys were tested on a ball-on-disk tribometer by rubbing against an alumina ceramic ball from room temperature to 600°C. The topography of the laser surface textured dimples was measured by a white light interferometer and optical microscope. The dimples are 150-200 μ m in diameter and 45-50 μ m in depth. The distance between the dimples is 500 μ m. The molybdenized layer is approximately 20 μ m in thickness. The elastic modulus of Ni-base alloy is improved by molybdenizing. After texturing and the molybdenizing duplex treatment, the friction coefficient of the Ni-base alloy decreases from 0.38 to 0.26 at room temperature and from 0.42 to 0.34 at 600°C. The wear rate of the duplex-treated alloy is much lower than that of the pristine alloy at 600°C due to the textured dimples storing lubricious oxides.

Microstructure and corrosion resistance of Fe-Al intermetallic coating on 45 steel synthesized by double glow plasma surface alloying technology

A binary Fe-Al alloyed layer was synthesized on 45 steel by means of double glow plasma surface alloying technique. The corrosion-resisting layer prepared is composed of a sedimentary layer and a diffusion layer, with a total thickness of about 180 μm. The aluminum content of the alloyed layer shows gradual change from surface to the inside of substrate. The ideal profile is beneficial to the metallurgical bonding of the surface alloying layer with substrate materials. The microstructure of both layers consists of the Fe-Al intermetallic compound, which is FeAl with B2 structure in the sedimentary layer and Fe 3Al with incompletely ordered DO 3 structure in the diffusion layer. The protective film exhibits high micro-hardness. In comparison with the substrate of 45 steel, the corrosion resistance of the aluminized sample is much higher in 2.0% Na 2S and 0.05 mol/L Na 2SO 4 + 0.5 mol/L NaCl mixed solutions.