Preparation And Performance Of Zirconium And Zirconia Alloyed Layers On TC4

TC4 has been widely used in aerospace,medical equipment and chemical industries due to its excellent strength to weigh ratio,high corrosion resistance and biocompatibility.But its application was limited due to the low hardness and deficient tribological property of TC4.In this work,Zr alloyed layers were prepared by double glow plasma surface alloying technique on TC4,and then the Zr alloyed layers were oxidized by MPCVD technique.The results show that alloyed layers are continuous and compact.The thickness,phase structure and surface microhardness were studied.The tribological property of TC4 and alloyed layers in air and artificial simulated saliva were compared and evaluated.The corrosion behavior of TC4 and alloyed layers were investigated in3.5%NaCl solution and artificial simulated saliva respectively.The biocompatibility of TC4 and alloyed layers were tested.The following conclusion were obtained:The continuous and compact Zr alloyed layers can be fabricated on TC4surface by using the double glow plasma surface alloying technique.The thickness of Zr alloyed layers increases with the alloying temperature increased.And the composition is in a gradient distribution.ZrO₂ alloyed layers were obtained after oxidation.Compared with TC4,both Zr alloyed layers and ZrO₂alloyed layers have higher surface microhardness and higher surface roughness.There are good bonding strength between the alloyed layers and substrate due to metallurgical bonding.The wear resistance of the alloyed layers are significantly improved compared with the substrate under different conditions.In the air condition,The wear rates of the alloyed layers decrease compared with TC4,especially the that of 850?ZrO₂-TC4,showing an excellent wear resistance.The wear mechanism of Zr-TC4 specimens was abrasive wear and oxidative wear.The wear mechanism of ZrO₂-TC4 specimens was micro-cut wear..In artificial simuated saliva,the friction coefficients and specific wear rates of TC4 and alloyed layers are lower than that of in air.The reason is that solution acts as a lubricant.The wear rate of Zr alloyed layers and ZrO₂ alloyed layers is significantly lower than that of the substrate.The wear rate of ZrO₂-TC4 at850°C is 3 orders of magnitude lower than that of the TC4,and the wear resistance is most significantly improved.In 3.5%NaCl solution,compared with TC4,the corrosion rate of the Zr-TC4 sample at 800°C was 55%lower than that of the substrate.The corrosion resistance of this sample was most obvious.Compared with Zr-TC4samples,the corrosion resistance of ZrO₂-TC4 sample at 800°C is improved.In the artificial simulated saliva,the corrosion potentials of Zr-TC4 sample and ZrO₂-TC4 sample are positively shifted compared with the substrate,and the corrosion current densities are all reduced.The corrosion current density of the ZrO₂-TC4 sample at 800°C reduces by 1 order of magnitude,corrosion rate decreases significantly,which show the most obvious improvement in corrosion resistance.In the electrochemical impedance spectroscopy,ZrO₂-TC4 has the largest capacitive arc radius at 800°C,the largest impedance value,and the phase angle is closest to-90°,indicating that the zirconia alloy layer has excellent corrosion resistance.In addition,the zirconia alloy layer has excellent biocompatibility and it is advantageous for the growth and proliferation of osteoblasts.