In this paper, two long-term experiments are conducted in order to investigate the evolution of the arc root fluctuations and the evolution of the in-flight particle state during plasma spraying. Voltage as well as the acoustic fluctuations measured at three different angles are characterized while particle state was monitored using an optical integrated system, the DPV2000. A detailed study of the evolution of the gun power, in-flight particle state (temperature, velocity, diameter, particle flux) and coating microstructure is was carried out. Results showed that the microstructure of the deposited coating significantly changed during the forty-hour spraying period. Paper includes a German-language abstract.

This paper describes the development of an online process control system for spraying thick thermal barrier coatings as part of a Brite Euram research project. In addition to the evaluation of the substrate temperature, a system for acoustic emission analysis for particle impact and for controlling crack propagation is developed. The procedure, the problems overcome, and the results obtained are described. Paper includes a German-language abstract.

Thermal spraying is a widespread coating process with various applications in many industry branches. To be able to spray successfully on the sensitive materials an in-situ temperature control is most beneficial. The objective of this paper is to find out the correlation between the mechanical properties of some coating-substrate variations and temperature history of the coating made by HVOF. The paper describes the processes involved in implementation of the thermographic measurement systems into the HVOF spray system to measure the temperature of the coating on aluminum and steel during spraying. It was observed that when spraying on aluminum, the temperature of the coating has a marked influence on the adhesion. Tests with a steel substrate show how the hardness of the WC-CoCr depends on the quenching speed of the coating during spraying. Paper includes a German-language abstract.

During the coating of components like rolls the major parameters are easily to control. But this is not sufficient to guarantee and stable a high coating quality. Additionally non-controllable parameters, e. g. nozzle wear, influence the process mainly. For this purpose a new testing method is necessary. On base of the acoustic emission analysis a testing equipment was developed in order to control the spraying conditions. In this investigation acoustic emission is applied to anlyse the signals generated by the impact of the molten particels on the component surface. The analysis of the signals is carried out in combination with a new classification method. The results of controlling APS(Atmosperical Plasma Spraying)-process during the disposition of a Cr2O3- coating will be presented. Paper text in German.

A reliable measuring tool of surface degradation can therefore result in substantial savings in time and money for the development of machine components, lubricants, wear resistant coatings, surface treatments process, and for the control/optimization of components life time during production sites maintenance. For this purpose, Thin Layer Activation (TLA) has much to offer since it makes possible to monitor in situ very small surface material losses under real operating conditions, often without the need of dismantling the working equipment. In this paper, an overview of the TLA technology is presented, which enables wear to be measured under real operating conditions by monitoring the loss of substance caused by surface degradation. It emphasizes the benefits that this technique can bring through already tested applications in the automotive, energy, and machinery industry. Paper includes a German-language abstract.

Novel thermal spray technologies must be thoroughly tested before they can replace the existing processes. In order to reproduce the properties of the accepted coatings, numerous test pieces must be sprayed and characterized by many different combinations of the available spray parameters. The method is time-consuming and often not very efficient. In this paper, a different approach is considered, whereby the state of the sprayed particles is characterized during the flight. The main objective is to examine the possibility to spray particles with similar in-flight characteristics with two different plasma guns in order to spray similar coatings with both guns. It is observed that the SM-F100 plasma gun can produce similar yttria stabilized zirconia particle jets as those sprayed with the F4-MB gun with 50% less electric power. Paper includes a German-language abstract.

This paper aims to achieve improved control over the spray pattern in a wire arc torch by means of constructive measures to influence the flow dynamics. It focuses on evaluating different fluid dynamic designs of the spray torches with respect to the droplet trajectories and velocity distributions and the deposit distribution. First, the paper describes the approaches for novel nozzle designs including the addition of shrouds and the torch evaluation diagnostics, and then presents the results for four different nozzle arrangements. It is observed that the nozzle design and the placement of the wire tips within the nozzle have the greatest effect on the divergence of the spray pattern. Paper includes a German-language abstract.

The quality and the deposition efficiency of coatings produced in thermal spraying processes are influenced by many parameters. Therefore normally the process optimization is laborious and time consuming. To reduce these efforts the low cost In-situ diagnostic method PFI was developed. A stationary CCD camera records the radiation of the hot propellant carrier-medium and of the luminous particle flux. A connected PC immediately converts the brightness distributions to a false colour image corresponding to the temperature and density profiles of the carrier-medium and of the particle flux. Utilizing a reference image the parameters can be adjusted for a prompt and successful optimization of the spray process. The performance of the PFI- method is demonstrated in some examples. Paper text in German.