Modeling of Thickness and Profile Uniformity of Thermally Sprayed Coatings Deposited on Cylinders
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Modeling of Thickness and Profile Uniformity of Thermally Sprayed Coatings Deposited on Cylinders Zhang Yanjun1 • Li Wenbo1 • Li Dayu1 • Xiao Jinkun1 • Zhang Chao1
Submitted: 5 June 2017 / in revised form: 30 October 2017 Ó ASM International 2017
Abstract In thermal spraying processes, kinematic parameters of the robot play a decisive role in the coating thickness and profile. In this regard, some achievements have been made to optimize the spray trajectory on flat surfaces. However, few reports have focused on nonholonomic or variable-curvature cylindrical surfaces. The aim of this study is to investigate the correlation between the coating profile, coating thickness, and scanning step, which is determined by the radius of curvature and scanning angle. A mathematical simulation model was developed to predict the thickness of thermally sprayed coatings. Experiments were performed on cylinders with different radiuses of curvature to evaluate the predictive ability of the model. Keywords coating thickness profile uniformity radius of curvature scanning angle thermal spray
Introduction Thermal spray technology includes a range of processes such as plasma spray, flame spray, arc spray, etc. in which feedstock materials (e.g., metal, alloy, ceramic, polymer, and composite materials) are deposited onto a substrate surface in molten or semimolten state to form stacked layers (Ref 1). Thermal spray technology is an important field of & Zhang Yanjun [email protected] & Zhang Chao [email protected] 1
College of Mechanical Engineering, Yangzhou University, Yangzhou 225127, China
surface engineering and one of the most important surface protection and strengthening technologies applied in the manufacturing of many durable products, such as automobiles, airplanes, and appliances (Ref 2). However, achieving uniform coating on cylinders remains a challenge due to the complexity of the surface geometry (Ref 3). Use of precise robot programs is required to ensure coating characteristics with low tolerance in terms of thickness, roughness, hardness, porosity, and coating microstructure. Many parameters of the thermal spray process affect the coating thickness and coating profile, including the scanning step, spray distance, spray angle, and traverse velocity of the spray gun (Ref 4, 5). To date, most research has focused on cylinders or surfaces approximating a circular column. In the traditional spraying process, planning of the spray path for this kind of surface is similar to that applied for a plane. The workpiece is rotated on the worktable at a certain speed, combined with a spray gun for thermal spraying. This can be considered equivalent to a simple unfolding of the cylinder. The planning of the spray path can also be referred to a plane. However, when the surface to be sprayed is part of a circular column surface, e.g., a nonholonomic or variablecurvature cylinder, this traditional method is not practicable (Ref 6, 7). Much work has been carried out on robot path planning for curved surfaces, s
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