This paper contributes to the broadening of knowledge about process combinations in connection with thermally sprayed coatings. It describes the influence of a later annealing, nitriding, and carburizing on different thermal sprayed coatings. The connection between the processes is determined and optimal process parameters is adjusted for both processes. The paper analyzes the coating characteristics and the alterations of the substrate. The results of the metallographic and X-ray analysis as well as of the wear and corrosion tests are discussed. Prospects for possible further applications are given. Paper includes a German-language abstract.

At the present, components which require both nitriding and locally a thermal sprayed coating or nitrided components which should l)e reworked are usually nitrided before spraying and the area to be coated is masked during nitriding or is prepared before spraying by locally removing the nitrided layer by grinding. Seen technically, advantages are to be expected if the nitriding process can be carried out after spraying. Moreover a post-nitriding of thermal sprayed coatings is of interest for improving coating characteristics, mainly wear resistance. Understanding the behaviour of sprayed coatings during nitriding in comparison to bulk materials will help to understand generally the behaviour of such coatings in gas atmospheres at increased temperatures. The objectives of the project are the investigation of the interaction between thermal spraying and nitriding, and the optimisation of both processes to achieve improved bonding, wear and corrosion characteristics respectively to get nitriding of the substrate through the coating without spalling or cracking. Furthermore the behaviour and structural changes of different coatings at increased temperatures are determined. The metallographic, X-ray, wear and corrosion results of the resulting compound coatings and parts are presented. Possible new applications are discussed. The project is funded by the German Research Ministry.