Property Of Metal Nitride Film On Magnesium Alloy By Arc Ion Plating

To compensate for the low corrosion properties and mechanical properties of magnesium alloy and promote the application of magnesium alloy in more fields. TiN coatings of different thickness and Cr/CrN multilayer coatings with different modulation period on magnesium alloy were prepared by arc ion plating. Ni coatings of different thickness on magnesium alloy were prepared by electroplating. The structure and properties of these coatings were studied in this paper.TiN coatings with better adhesion strength were prepared on magnesium alloy by arc ion plating. The TiN coatings contain fcc structure TiN phase and possess obvious (111) preferred orientation. The thickness of TiN coatings first increases and then decreases with increasing negative bias. The coatings at 150V negative bias have the maximum thickness of 8μm. The relation of hardness of TiN coating to negative bias is similar to ones of thickness. The highest hardness of 2042HV also appears in the coatings at 150 V negative bias. Polarization curve show that corrosion resistance increase with increasing negative bias. The highest corrosion resistance appears the coatings at 150 V negative bias because they have little large particles on coating surface and the ratio of Ti to N on coatings is near 1. The Cr/CrN multilayer coatings with different modulation period can be prepared on magnesium alloy by arc ion plating by adjusting the time ratio (min: min) of Ar gas and N₂ gas in chamber. The SEM results confirmed the clear periodicity of the Cr/CrN multilayer coatings and clear interface. The XRD patterns measured revealed that these multilayer coatings contain CrN phase and a little Cr and Cr₂N phase. The CrN phase in the coatings has obvious (220) preferred orientation. Under condition of the 2 min Ar gas. The hardness of the Cr/CrN multilayer coating increases with increasing the time of N₂ gas in environment. The highest hardness of 2656HV appears at the time ratio of Ar and N₂ gas of 2:8. Polarization curve of Cr/CrN multilayer coatings show that the corrosion resistance of all samples with multilayer coating is higher than ones of sample without coating. The corrosion resistance increase with decreasing the time of N₂ gas in environment. However, although the corrosion resistance of sample is improved by the depositing the TiN or Cr/CrN coatings, the improvement of corrosion resistance is not very high. It is an effective method to increase the corrosive resistance of magnesium alloy that electroplating Ni coatings on magnesium alloy by depositing Cu interface by arc ion plating.