For coating increasingly complex geometries that require a high accuracy with respect to a near net-shape coating distribution, the use of computer-aided path planning algorithms is mandatory to minimize the need for expensive prototyping experiments. During the planning process, coating simulations are typically evaluated frequently, thus both fast and accurate simulations greatly enhance the potential to find optimal path solutions. In this contribution, an efficient approach for computing the coating thickness on complex workpieces is presented, which makes use of the computational capabilities of mainstream graphics hardware to achieve simulation times well within the single-digit range of seconds for average-sized workpieces. Using a semi-automatic, measurement-based calibration routine, this simulation can easily be adapted to different processes. The simulation has been coupled with a path-optimization approach and was successfully utilized to enhance the deposition accuracy in the context of applying wear-resistant coatings to deep-drawing tools by means of a TWAS process.

With appropriate process control, near-net-shape coatings can be successfully applied to parts with complex geometries using HVOF spraying and fine cermet powders. This study assesses the influence of critical process parameters on the deposition rate and properties of HVOF coatings produced using fine agglomerated WC-12Co powder (2-10 µm) with nanosized WC particles. Spray angle, standoff distance, gun velocity, track pitch, and backside air cooling pressure were varied during the experiments in order to determine their effect on coating hardness, roughness, and porosity as well as deposition efficiency. Variations in spray parameters were found to have a significant effect on deposition rate and coating properties.

The aim of this study is to determine how various factors, including process parameters and nozzle configurations, affect the shape and size of the spray jet in twin wire arc spraying. In the experiments, steel specimens were sprayed using an iron-based cored wire with a fused tungsten carbide filling. In-flight particle temperature and velocity and fluctuations in voltage and current were measured during spraying. The shape of the thermal spray spot and the 3D footprint of the plume were determined by means of image analysis and tactile surface profiling methods. The results obtained show that spray plume characteristics, and thus particle distribution, are heavily influenced by secondary gas flow, particularly the number, location, and angle of atomization outlet holes in the secondary gas nozzle.

In this study, a path strategy for robot-based HVOF spraying is developed via deposition simulations. The simulations include the analysis of the spray plume footprint and the consideration of robot dynamics in the path planning strategy. A fine WC-Co powder was used as the feedstock material.

This study investigates the influence of component geometry, particularly the outer radius of curved surfaces, on the hardness and porosity of HVOF-sprayed WC-Co coatings as well as the deposition rate. A fine agglomerated and sintered WC-12Co powder of spherical shape was sprayed on steel substrates. Process parameters were held constant, while the radius of curvature was varied between 5 and 40 mm. The results show that HVOF spraying is better for depositing fine particles on curved surfaces than other spray processes, although the deposition rate decreases compared to flat substrates.

Computer simulations of thermal spray coating processes can accelerate the development of new products by minimizing the need for prototypes. An important aim of these simulations is the calculation of the coating distribution on the surface of a given workpiece with respect to a given movement path of the spray gun. In this paper, a novel approach for computing coating distribution on arbitrarily complex freeform surfaces is presented. In contrast to approaches that implement symmetric deposition models, the presented concept is based on a rotationally asymmetric model, making it particularly well suited for wire arc spraying as turbulences caused by electrodes in the gas flow often result in asymmetric coating distributions. In order to obtain the required knowledge base to derive the deposition model and verify the simulation, basic experiments were made. The simulation concept and experimental setup are presented in the paper along with the results.