[Show abstract][Hide abstract] ABSTRACT: Polycrystalline diamond films were grown on WC–Co substrates by microwave assisted chemical vapor deposition using a gas mixture of hydrogen, oxygen and methane. The diamond coated WC–Co substrates were processed at high pressure (7.7 GPa) and high temperature (1000 °C) and their mechanical behavior was investigated by hardness instrumented testing before and after the high-pressure/high-temperature (HPHT) processing. The results indicated the diamond films became less friable after the HPHT processing, probably due to the infiltration of Co from the substrate. This conclusion was corroborated by corrosion tests performed with the samples before and after the HPHT processing.
Surface and Coatings Technology 08/2009; 203(22):3344-3347. · 2.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new, low cost, pulsed-DC plasma-enhanced chemical vapor deposition system that uses a bipolar, pulsed power supply was designed and tested to evaluate its capacity to produce quality diamond-like carbon films on the inner surface of steel tubes. The main focus of the study was to attain films with low friction coefficients, low total stress, a high degree of hardness, and very good adherence to the inner surface of long metallic tubes at a reasonable growth rate. In order to enhance the diamond-like carbon coating adhesion to metallic surfaces, four steps were used: (1) argon ion sputtering; (2) plasma nitriding; (3) a thin amorphous silicon interlayer deposition, using silane as the precursor gas; and (4) diamond-like carbon film deposition using methane atmosphere. This paper presents various test results as functions of the methane gas pressure and of the coaxial metal anode diameter, where the pulsed-DC voltage constant is kept constant. The influence of the coaxial metal anode diameter and of the methane gas pressure is also demonstrated. The results obtained showed the possibilities of using these DLC coatings for reduced friction and to harden inner surface of the steel tubes.
Journal of Nanoscience and Nanotechnology 05/2009; 9(6):3891-3897. · 1.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Surface and bulk properties of diamond-like carbon (DLC) films prepared by using different techniques and under different conditions have been of great concern. The main focus is to reach low total stress, high hardness, high adherence, and low friction coefficient, including the deposition in large area at high growth rate. In this work, DLC films were obtained by using a low cost modified pulsed-DC discharge technique. Different pulse bursts with different pulse widths and delay times were considered. Studies have been carried out in order to match the best set of parameters as mentioned above for different applications, as required in the frame work of our project. The DLC films were deposited onto Si(100) and 304 stainless steel substrates. A thin amorphous silicon interlayer was used to reduce the DLC film's total stress and to improve the films' adhesion to the substrates. A summary of the deposition rates, structural, mechanical, and tribological properties as functions of the pulsed-DC voltage and pulse characteristics will be presented. The results show that the adhesion of the DLC coatings on stainless steel using a thin amorphous silicon interlayer could be improved significantly.