Coating Characterizations and Evaluation of Ceramic Metal Mixture Slurry Based Thermal Barrier Coating for Automotive Turbocharger Turbine Application

Abstract

Turbocharging the internal combustion engine (ICE) is to increase the power density of the engine or known as the downsizing of the engine. Large amount of heat energy is wasted through the exhaust manifold, coolant, convective and radiate heat transfer. The amount of heat loss generated to the surrounding by operating turbine volute will affect the service life of some automotive components. The current material tungsten used for heavy duty automotive turbine volute casing is heavier and costly if to compare to a new suggested material nickel with thermal barrier ceramic coating as an alternative. Thermal barrier coating is an alternative method for insulating cheaper and lighter engineering components operating in extreme temperature condition, there exist different coating techniques, but high installation cost and high technical skills requirement have restricted their widespread acceptance. The need of simple and cost effective thermal barrier coating has become necessary for the alternative coating method. In this study, slurry based coating method was adopted and the Ni/Basalt slurry mixture was coated by using an automatic film applicator in order ensures a uniform thickness of the coating. Appropriate amount of nickel powder and basalt fibre were mixed to produce the slurry mixture. A composition of 70wt% nickel powder and 30wt% basalt fibre was used in depositing the thermal barrier coating layer on nickel substrate. The coating microstructures were analyzed and evaluated by using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). The coatings were also examined with EDX line (Energy Dispersive X-ray Spectroscopy) in order to determine the phases formed during the coating process. The mechanical properties including adhesion strength and Vickers micro hardness were measured. The results shown that the Ni/Basalt slurry based coating was suitable and appropriate for the coating process of the substrate as an application in the inner passage of the casing.