This paper analyses the influence of specific coating parameters such as robot velocity, spray distance and part cooling on the risk of crack formation within Chromium- Carbide / Nickel-Chromium coatings. To understand the effect in more detail, metallographic investigations were conducted. These also provide sufficient data to examine other important coating characteristics such as porosity, mechanical stresses and homogeneity. As an additional analytical method Element Mapping is utilised to show the level of oxidation and its impact on the coating microstructure. The methods X-ray diffraction (XRD) and In-situ coating property (ICP)-Sensor are used to investigate the development of stresses in different coatings. With the information from all these examinations a concept was derived to achieve thick, crack-free wear protective coatings.

High temperature oxidation behavior of MCrAlY coatings was studied at several temperatures in the range from 800 to 1100°C. In this study the MCrAlY coatings were obtained by plating using CrAlY as precursor powders in an electrolytic bath containing nickel and cobalt salt in solution. The size of the precursor CrAlY powders used was generally below 10 um. As-plated coatings consisted of a random distribution of CrAlY particles in the Ni-Co matrix. The heat-treatment of the as-plated coatings at elevated temperature resulted in the development of a gamma and beta structure. Both as-deposited and oxidized coatings were characterized by optical, scanning electron microscope and electron beam microprobe. During oxidation the coatings formed alumina scale with a negligible amount of transient nickel and chromium oxides. The spallation resistance of the oxide scale was investigated by thermal shock testing. The test consisted of a rapid cooling from 1000°C to 100°C with a two- minute dwell time at the maximum temperature. The thermal shock test was conducted in a) as–deposited and heat-treated condition and b) after preoxidation at 800°C and 1050°C, respectively. The coatings retained the alumina scale during thermal shock cycling.

MCrAlY bond coats were deposited on nickel base substrate by electroplated process. The bond coats were plated using ‘CrAlY’ precursor powders suspended in an electrolytic bath containing nickel and cobalt in solution. The CrAlY powders used had size in the range generally below 10 um. The as-deposited coatings were heat-treated in a vacuum at elevated temperature. The roughness of the as-deposited coatings was on the range from 2 to 4 um (average). Yttria stabilized zirconia thermal barrier coatings, 7YSZ were deposited by air plasma spray. The thickness of the both bond coats and TBCs was varied in order to determine the effects of thickness in the stability of the thermal barrier coatings. The coated samples were tested in a static furnace and also in a thermal shock test rig where the samples could be cooled rapidly from 1000°C to 100°C at a predetermined rate. The TGO formed at temperatures in the range from 800 to 1050°C was characterized by optical, scanning electron microscope and electron beam microprobe.