Chemical and Materials Engineering 3(2): 29-37, 2015 http://www.hrpub.org DOI: 10.13189/cme.2015.030203 Effect of Plasma Enhanced Chemical Vapor Deposition of Tetraethylorthosilicate on the Friction and Wear Loss of Plasma Electrolytic Oxidized Aluminum 6082 Ahmad R Rastkar Laser and Plasma Research Institute, Shahid Beheshti University, Iran Copyright © 2015 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract The surface of 6082 aluminum alloy was coated by plasma electrolytic oxidation (PEO) and then treated by plasma enhanced chemical vapour deposition (PEVCD) of tetraethylorthosilicate (TEOS), oxygen and argon. The PEO electrolyte was alkaline and consisted of potassium hydroxide and sodium aluminates. A pulsed DC power supply with the frequency of 18 kHz was utilized to perform PEO and PECVD treatments. In the PEO process, the electrolyte was at boiling temperature. PECVD was carried out at temperature of 400°C. The working pressure of vacuum chamber was 10 mbar. The surfaces were characterised using XRD, optical, AFM and SEM microscopy, EDX analysis, Vickers microhardness test and ball on disc wear test methods. The thickness of PEO coated layers was more than 80 μm. α-Al 2 O 3 was the main oxide compound in the coatings. PECVD treatment resulted in the diffusion of silicon in the surface oxide layer. However, up to 16% silicon was identified in the top surface layers after PECVD treatment, no considerable variation in the thickness of the alumina layer or new layers were observed on the surface of the samples. PEO coating generated very hard surfaces with highly varying coefficient of friction. PECVD treatment reduced the hardness slightly, modified the friction behavior and reduced the wear loss several times. Keywords Adhesive Wear, Surface Roughness, Hardness, Coating, Wear Resistance, Stick-slip 1. Introduction Industrial applications are demanding wear resistant light alloys, such as surface treated aluminum alloys, instead of steel. This requires surface hardness of more than 700 HV. Hard anodizing has been experienced as one the methods for improving the surface properties of light alloys. After hard anodizing the surface hardness and the wear resistance of coatings on aluminum are not as high as hard resisting layers on steel [1]. PEO has offered new developments in aluminum oxidation. Several studies have attempted to produce uniform oxide layers on Al alloys with conventional anodizing or PEO processes in different electrolytes. Nevertheless, researchers have yet to produce a uniform and dense oxide layer free from surface porosities. Spark discharges in PEO process create discharge channels on the surface of the samples. Melting, oxidation and ejection of the elements in these channels lead to growth of the nano or microcrystalline structure of the coating [2, 3]. This technique is also named micro-arc oxidation. The plasma phenomena in micro arc oxidation (MAO) or Plasma electrolytic oxidation (PEO) give unique effect to the coatings which increase the life of industrial parts with favorable properties such as high hardness and anti-corrosion abilities [4, 5]. Industrial applications of these coatings are widely ranging from automotive to aerospace, textile and oil and gas industry [6]. Aluminum oxide coatings do not show low or smooth friction behavior on the surface of aluminum alloys. Sometimes the high coefficient friction or in fact stick slip friction behavior of these coating may result in localized wear or spallation of oxidized surfaces. It has been found that PEO of Al–Si alloy with 7% silicon content in alkali silicate solution mainly result in the formation of α-Al 2 O 3 , γ-Al 2 O 3 and SiO 2 and some percentage of mullites (3Al 2 O 3 -2SiO 2 ) in the coating. These investigations have shown that different combinations of α-Al 2 O 3 and SiO 2 reduce the friction on the alumina surfaces [7]. It is proposed that it would be beneficial to produce mullites like phases or combinations of α-Al 2 O 3 and SiO 2 on PEO surfaces to reduce the friction coefficient of oxide layer and consequently increase the wear resistance of these surfaces. It has been observed that oxides deposited from organosilicates compounds such as tetraethylorthosilicate (TEOS) show low friction properties on the surface of light alloys. Therefore, in this paper we have studied the effect of