Benzene flow rate effect on the properties of carbon films deposited on plasma nitrided steel using the MW/ECR PACVD process

摘要

Amorphous hydrogenated carbon a-c:H films often called DLC films were deposited on plasma nitrided layers of Z30C13 steel substrate using the Microwave Electron Cyclotron Resonance Plasma Assisted Chemical Vapour Deposition method with benzene/argon gas a precursor. The coatings were deposited on ferrite and (F) Fe2-3N at different temperatures: 623, 753 and 793 K for time intervals between 2 up to 120 min under different pressures ranging from 10(-3) to 10(-1) Pa. A wide range of thickness values of the amorphous carbon layers (0.4 up to 15 mum) was formed a function of the deposition conditions and precursors, when the bias voltage (-200V) and microwave power (300 W) were kept constant. However, pretreatments consisting in mechanical polishing down to a surface roughness Ra< 0.06 mum, with ultrasonic cleaning and plasma argon etching of the substrates before depositing were necessary for sufficient adhesion of the coating., For a gas mixture of benzene and argon with 10 sccm and 20 sccm flow rates, respectively, analysis by scanning electron microscopy (SEM) showed a poor adhesion and carbon films delamination. Nevertheless, the best adhesion of hard coatings to the nitrided layers was achieved when the benzene flow rate was reduced to 4 sccm. Scratch tests revealed that they possess excellent resistance strength (10 to 81 GPa) and exhibit both low values of coefficient of friction (0.03 to 0.3) and roughness (0.05-0.24 mum). The Improvement in the carbon films adhesion to the nitrided layers is seen from X-rays diffraction as due to an interlayer formed mainly of phases such as Cr-23 C-6, (Fe,Cr)(7)C-3, (Fe,Cr)(3)C and Cr3C2. [References: 21]