Comparison of radio frequency and pulsed-d.c. plasma CVD of Ti-C-N-H and Zr-C-N-H layers at low temperature

The coating of aluminium alloys with Ti-C-N-H and Zr-C-N-H layers by a plasma assisted CVD technique using metal-organic compounds of the type tetrakis(diethyl)-amidometal (Me(N(C2H5)2)4) was investigated. A radio frequency (r.f.) and a pulsed-d.c. excitation was used in this study for the generation of the plasma. The layer properties were compared for the different plasma sources. The chemical composition of the deposited layers depends on the plasma source and on the process parameters, e. g. plasma power. The metal content in the layers was increased whereas the carbon and hydrogen content was decreased by using pulsed-d.c. plasma compared to r.f. plasma. The layers had homogeneous composition over the layer thickness. The hardness of the Ti-C-N-H as well as Zr-C-N-H layers was between 1500 and 1900 HK0.005. The coatings had a high wear resistance measured by a ball cratering grinding test and a low friction coefficient of 0.2.