Although substrates are often grit blasted prior to thermal spraying to improve coating adhesion, the relationship between surface roughness and bond strength is not well understood. This paper proposes a new method for characterizing the surface roughness of substrates on the hypothesis that mechanical friction between the coating and substrate primarily determines adhesive strength. The authors explain how they measure 3D surface profiles using a confocal scanning microscope and develop the necessary math to calculate friction forces and coefficients. They also present experimental results comparing the roughness of stainless steel and aluminum substrates with the adhesive strength of plasma-sprayed Al 2 0 3 layers. Paper includes a German-language abstract.

One of the key aspects of particle behavior in the plasma jet is the stochastic nature of the injection process. Particles are injected into the plasma jet with a certain variation in initial velocity which, along with their size distribution, determines the form of the layer structure and the degree of melting. The aim of this work is to model the influence of the initial spray parameters on the main characteristics of spray particles, such as temperature, velocity, and degree of melting, during impact with the substrate. A one-dimensional heat conduction equation that accounts for phase transitions is solved numerically for spherical particle shapes. The dynamic particle problem is also solved and an integral criterion for the coating model is obtained. Paper includes a German-language abstract.

The aim of this work is to develop a finite element model that predicts the residual stresses in plasma sprayed parts formed on conical mandrels and removed by various means. The theoretical analyses and mathematical models are confirmed by X-ray diffraction measurements on plasma-sprayed zirconia samples freed from shaped mandrels by means of cooling, melting, and chemical dissolution. Based on test results, the mandrel-cooling removal method produced the highest internal stresses. Paper includes a German-language abstract.