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Influence of spray kinematic parameters on high velocity oxy-fuel sprayed WC-Co coatings’ properties applied on complex geometries.

Katranidis, Vasileios (2018) Influence of spray kinematic parameters on high velocity oxy-fuel sprayed WC-Co coatings’ properties applied on complex geometries. Doctoral thesis, University of Surrey.

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As the regulatory limitations of hard-chrome plating surge, the successful application of thermal- sprayed wear/corrosion resistant coatings on complex geometries becomes critical. Thermal spraying is a line-of-sight method and thus, spraying a complex geometry results to changes in the spray angle, the spray distance and the effective gun traverse speed. Although there has been some research on the effects of these kinematic parameters on the coatings, previous work tends to examine the kinematic parameters in isolation, disregarding of any interplay between them. Yet, the effective particle velocity at impingement is dictated both by spray angle and spray distance while the particle temperature is mainly dictated by spray distance. In addition, the heat and mass transfer to the underlying coating are controlled by the gun traverse speed. These facts suggest that significant synergistic effects are expected when the spray kinematic parameters vary simultaneously, as when a complex geometry is sprayed. This work aims at evaluating the systemic effect of the spray kinematic parameters on WC-Co coatings sprayed by HVOF. Various coating properties are comprehensively examined and discussed, exploring the microstructures, phase composition, mechanical qualities and tribological performance. Significant interplay between the spray kinematic parameters is demonstrated in a number of coating properties, yielding non-linear behaviours. The notable beneficial role of small spray angle inclinations at long spray distances, in regards to deposition rate, microstructure, microhardness and wear resistance is demonstrated. Mechanisms of the particle rebounding, superficial oxidation of the coating, metallic tungsten crystallization, tribofilm formation and wear damage progression are proposed, with respect to the spray kinematic parameters. Finally, an attempt to generalize the insights from this work to any given sprayable geometry takes place in a prototype software tool in Matlab.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors :
Katranidis, Vasileios
Date : 31 July 2018
Funders : University of Surrey PhD studentship
Projects : University of Surrey PhD studentship
Contributors :
Uncontrolled Keywords : Thermal spray, Coatings, spray kinematic parameters, spray angle, complex geometries, WC-Co, wear resistant coatings, carbides
Depositing User : Vasileios Katranidis
Date Deposited : 06 Aug 2018 08:27
Last Modified : 09 Nov 2018 16:39

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