Investigation of Wear and Corrosion Behaviour of AISI 316 L Stainless Steel Coated By ESD Surface Modification

Abstract

AISI 316 L austenitic stainless steel is widely used in various sectors of the industry (chemical, petro-chemical industry, paper industry, nuclear engineering, dairy equipment and medical field) because of its good corrosion resistance and biocompatibility. In contrast to these superior properties, it has a low hardness and poor wear performance, thus, limiting its use in some areas of industry. As a result of progress in science and technology, the expectation of superior properties from materials has increased and the surface modification has become an important part of this development. Amongst many coating processes, Electro-spark Deposition (ESD) is a micro-bonding process that is used to deposit a stronger, more robust and durable coating layer on a metallic substrate. This method can also be used to repair damaged parts, tools or equipment or to extend the tool and equipment life. In this study, the surface of AISI 316 L stainless steel was coated with WC and Ti6Al4V by ESD method. Morphology and microstructure of the deposited layers were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Surface hardness distributions were determined with a micro hardness tester. XRD analysis revealed that Fe–α, Fe–γ, W2C, Cr–Ti, Al–Fe–Ti phases exist on the deposited layers. The wear behavior of the coated surfaces was carried out by ball-on-disc wear method using WC-Co ball bearing with a diameter of 8 mm for a sliding distance of 250 meters at a sliding rate of 0.3 m/s under a dry condition using a load of 5 N. Corrosion behavior of coated surfaces i.e. Tafel extrapolation and linear polarization methods were investigated for the duration of 1 h in the SBF (Simule Body Fluid) solution. Morphology of layers formed on steel surface was examined by SEM microscope. Wear tests showed that AISI 316 L stainless steel has a low surface hardness but wear resistant coatings improved this property. The wear rate of coated AISI 316 L stainless steel decreased by 3–10 times with respect to the type of coating. The electrochemical experiments showed that the expected improvement was not achieved due to the high corrosion resistance of AISI 316 L stainless steel. However, the weakness of the surface hardness was partly replaced by an acceptable compromise from corrosion resistance.