Low temperature coating of aluminium alloys by Plasma-CVD using metalloorganic compounds

The deposition of Zr(C, N) layers on the aluminium alloy AlMgSil by the pulse DC PACVD technique using the metallo-organo compound tetrakis (diethyl) amidozirconium (Zr(N(C2H5)2)4) in H"-N2-plasmas is described. the deposition temperature could be lowered down to 150 degrees C. The content of carbon and nitrogen is extremely dependent on the process parameters. The hardness of the layers reached up to 1.400 HK. Polymeric carbon incorporated in the layers reduces the hardness of the layers. The plasma is investigated by the optical emission spectroscopy (OES) during the coating process. Ionized atomic zirconium, atomic carbon in the neutral and ionized state, carbon-containing molecules (CH, C2) and atomic and molecular nitrogen are detected. The dissociation of the metallo-organic compound is strongly influenced by the hydrogen content in the process gas and the discharge voltage.