A components surface determines its properties of interacting with the environment, independently if it is solid (friction on another component), fluid (heat transfer in a heat exchanger) or a mixture of phases (wetting behavior). The properties of the surfaces that give a component a specific function have been studied at the Institute of Particle Process Engineering for more than 10 years. The plastic deformation of a surface due to single cold sprayed particles and high pressure water jets is investigated by numerical and experimental methods. A strong focus of our research lays on the surface characterization. With Scanning Electron Microscopy and Scanning Probe Imaging surface topographies are analyzed precisely. By nanoindentation the mechanical properties of a component close to its surface can be obtained at temperatures up to 800°C. Another focus is on the characterization of the interaction between particles or droplets and surfaces, related to the surface morphology.