Internal coating of cylinders has always been a challenge for cars engineers. Driven for more than two decades now by the ecological and economical constrains applied to the automotive industry, it constitutes a dynamic way of research and development for industrial applications. One of the most economical processes for this kind of coatings is the rotating twin-wire arc spray (TWAS) system. Meanwhile the actual quality and the performances of the corresponding coatings still leave place for some improvements. Therefore, in the work presented here, attention was paid to the second atomization phenomena in a TWAS system considering the influence of the gas flow parameters on the particles’ morphology and deposition behavior. Numerical modeling of the plume and comparisons between several designs of the second atomizing units were also considered.

Off-line programming software is widely used to simulate the robot-assisted work environment. RobotStudio, a product of ABB, offers off-line programming technology for industrial robot applications. Several software products that extend RobotStudio capabilities have been developed to meet special purposes. One such product is the Thermal Spray Toolkit. With the help of TST, RobotStudio can load the mesh information generated by ANSYS analysis software and then create the trajectory of robot spray operations with it. A method of arranging the index of grid nodes generated by ANSYS software is described in this article. The results show that TST can be successfully used to create a smooth robot trajectory, which corresponds to the requirements of industrial applications.

Reconstituted nanostructured and conventional yttria partially stabilized zirconia (YPSZ) coatings were deposited by atmospheric plasma spray. The tribological properties of the coatings against 100C6 steel were evaluated with a ball-on-disc configuration under dry friction conditions at room temperature. Microstructure and the phase composition of the powders and the coatings were examined using SEM, optical microscope (OM) and X-ray diffraction (XRD). Microhardness, Young’s modulus and fracture toughness of coatings were measured by indentation test. Results showed that the wear resistance of the coatings produced using the nanostructured powder is improved compared with the coating produced using the conventional powder. The wear rates of nanostructured zirconia coatings are about four-fifths of those of conventional counterparts under a load of 5 N. The wear mechanism is also discussed.

Disk-shaped splats that can be obtained on a heated substrate reveal a better contact with the substrate surface, resulting in a better adhesion/cohesion of coatings. Some research results illustrate that when the substrate temperature exceeds the transition temperature, the ideal splat can be obtained. In the simultaneous preheating-spraying-cooling process, named HEATCOOL in which a preheating gun heats the specimen just before the spraying and a cooling jet cools it just after the spraying, the preheating temperature is of short duration. In order to study the preheating effect and determine the optimal velocity of the movement of the system for obtaining an appropriate preheating temperature, the function specification method, an optimisation method, was adopted combined with FEM (the finite element method). An oxy-acetylene flame was used as preheating thermal resource, the optimal velocities were estimated. Particle impact tests of Cu and YSZ (ZrO 2 - 8%Y 2 O 3 ) powders sprayed by plasma with a flame heating system were carried out with different moving velocities. The splats morphology collected on stainless steel and aluminium plates were observed to clarify and confirm the calculated results.

It is necessary to cool specimens during spraying in the case APS or HVOF, because process-induced heat rises the specimen temperature and leads to oxidation and spalling of coatings. A reasonable cooling just after spraying improves some properties such as microhardness, adhesion and cohesion of the coating/substrate system. In the modelling of specimen temperature and residual stress, it is necessary to know the flux distribution of the cooling jet like compressed air, CO 2 liquid jet etc. Therefore, the evaluation of the flux becomes important. In order to measure and analyse the distribution of cooling flux imposed on the substrate, the theory of the inverse problem of heat conduction was applied and an experimental apparatus was designed to mesure the transient temperature. Because of its insensibility to the effect of measuring error, the conjugate gradient method, an effective method of inverse problems was chosen among several mathematical optimisation methods. The flux distributions of cooling jet can be estimated by using the measured data and a program written according to the conjugate gradient method.