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Cathodic Cage Plasma Deposition of DLC Film on D2 Steel Substrate

De Sousa RRM, Carvalho Costa TH, Da Costa JAP, Dos Santos FEP, Nascimento IO, Souzab IA and Viana BC

A diamond-like carbon (DLC) film was deposited on AISI D2 substrates by a cathode cage plasma deposition technique using a plasma nitriding surface treatment/nitriding system, assembled with a graphite cage. The deposition was done at a temperature of 450°C, in a gas mixture of Ar (25%)+H2 (75%) with a deposition time of 5 hours under a constant pressure of 2 mbar. The structural analysis using SEM and optical microscopy revealed the existence of material islands arranged as clusters of approximately 20 μm in diameter, while the layer obtained has a thickness of around 4 micrometers. Microhardness tests showed hardness values of around 1300 HV, a figure much higher than that of the substrate (250 HV). With the aid of X-ray diffraction, peaks were identified as Fe3C (cementite) and carbon, in the diamond phase (DLC). Raman spectroscopy was performed in two regions: in the islands and outside them. In the islands Raman peaks from a highly crystalline structure, identified as DLC, were observed and, around these islands, those from an amorphous region identified as amorphous carbon (a-C) were seen. It was concluded that the plasma deposition process using graphite cathodic cage generated an amorphous carbon coating with crystal islands of DLC on D2 steel substrate.