Abstract
High-velocity oxygen-fuel (HVOF) thermal spraying is a coating process involving multidisciplinary aspects, e.g., fuel–oxidant combustion, flame–particle jet, particle deposition, mass and heat transfer, and even robotic kinematics. Like most coating processes, in HVOF processes, coating thickness is a significant property determining the coating performance; hence, this property should be accurately controlled during the process. In view of green, smart, and digital manufacturing, the coating thickness prediction model is demanded to produce high-quality coatings efficiently. This paper presents an approach to parametrically simulate the coating thickness in HVOF processes via an integrated numerical model. Firstly, an axisymmetric computational fluid dynamics (CFD) model is constructed to compute the behaviors of the fuel–oxidant combustion, flame–particle jet, and particle deposition distribution. Secondly, based on the particle distribution in a 2D axisymmetric model, a 3D single coating thickness profile model is developed by constructing a circular pattern using the axis of the nozzle. Further, this profile is smoothened by a Gaussian model, and its mathematical expression is obtained. Finally, a numerical model couples spray paths with the mathematical expression to model the coating thickness distribution on a substrate surface under industrial scenarios. At the end of this paper, to verify the proposed model’s effectiveness, four sets of operating parameters with a single straight path were experimentally implemented. The width and height of the bead-like shape coating were in good agreement with the simulated results. The normalized root-mean-square errors of the cross-sectional profile heights were around 10%.
Highlights
High velocity oxygen-fuel (HVOF) deposition is a thermal spraying technology used to coat a protecting layer to improve the workpiece surface performance [1]
As this paper aims to propose a parametric model for constructing the coating thickness that is specific to HVOF processes, the review of the related works is divided into two parts, numerical modeling of HVOF thermal spraying and coating thickness modeling
This article contributes to an integrated numerical model for simulating the coating thickness in HVOF processes by linking spray paths with the Guassian coating profile
Summary
High velocity oxygen-fuel (HVOF) deposition is a thermal spraying technology used to coat a protecting layer to improve the workpiece surface performance [1]. It is a multidisciplinary process involving chemical reaction, turbulence, compressible flow, multiphase interactions, subsonic/supersonic transitions, and droplet deformation [2]. According to the studies of the coating formation mechanism [3, 6, 7], the coating formation is predominantly determined by the in-flight particle behavior near the substrate surface, which in turn is affected by the operating parameters, like the gas flow rate, the fuel/oxygen ratio, and other various operational conditions, like the spray systems used, substrate shape, and the fuel/oxidant types [7, 8]. The macrostructure of the coating is affected by the parameters relevant to the movement, e.g., scanning speed, scanning step, and spray distance [9, 10]
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