Microwave atmospheric pressure plasma for surface treatment and reactive coating on steel surfaces

The microwave atmospheric plasma technology developed at DANA corporation has previously been used for various heat treatment applications. In this paper, we demonstrate the use of atmospheric plasma assisted chemical vapor deposition (APACVD) process to coat steel surfaces. The method described in this paper involves two steps. The first step is to coat a Si based interlayer and then to coat C either by CH4 or C2H2 containing plasma. At the end of the coating process, a thick, colorful, reactive coating is formed on the steel surface. The XRD and compositional analyses have established the presence of metal carbide phases such as Cr7C3, Fe15.1C in these coatings. These phases are well bonded to the steel surface with no separate interlayer formation. Hardness tests show that carbide phases formed in a nitrogen containing plasma are 2.5 times harder compared to the bulk. The faster deposition rates at atmospheric pressure clearly indicate that this process is not only rapid (∼ 0.2 μm/min) but also cost-effective.