On the role of particle state and deposition procedure on mechanical, tribological and dielectric response of high velocity oxy-fuel sprayed alumina coatings
E. Turunen, T. Varis, S.-P. Hannula, A. Vaidya, A. Kulkarni, J. Gutleber, S. Sampath, H. Herman
Materials Science
Abstract
It is well known that the high velocity oxy-fuel based thermal spray process impart high density and reduced porosity in coatings compared to those produced by other ambient thermal spray processes. The benets of HVOF have largely remained in the domain of metals and cermets and limited investigations have been carried out in ceramic coatings. The ability to produce high density ceramic coatings (e.g. alumina) offers potential in high performance applications in the eld of wear, corrosion resistance and dielectric coatings. However, due to extreme operational limits of the HVOF process, the fundamentals of process structure property relationships are not fully understood. In this paper, we report an integrated approach to establish processing microstructure property correlations in order to optimize coatings for such applications. This approach involves diagnostic studies, microstructure development and its resultant inuence on properties of high velocity oxy-fuel (HVOF) sprayed alumina coatings. The diagnostic studies were aimed to investigate the effects of fuel gas/oxygen ratio and amount of total gas ow on the particle temperature and velocity. Furthermore, splats and coatings were deposited to investigate the relationship between diagnostic data, melting behavior and droplet substrate interactions. Such a comprehensive study, coupled with property measurements of the coatings, demonstrates critical operational variables among deposition procedure, coating microstructure and the deposit properties.
Keywords:Thermal spray; Mechanical properties; Alumina; HVOF; Diagnostic; Process optimization; Thermal and electrical properties
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