Plasma facing materials (PFMs) in a fusion device like ITER/DEMO have to withstand severe environmental conditions such as high thermal loads and particle fluxes. These exposure conditions may cause a deterioration of the heat removal capability of the material and/or component. In order to ensure that designs of plasma facing components are suitable for an application under such exposure conditions detailed qualification programs are required. Especially the high steady state and transient thermal loads, simulated with electron/laser beams and linear plasma devices, induce a wide range of surface modifications and damages on the PFM surface as well as in the component. Important issues are the performance of materials under high cycle transients, after/during neutron irradiation, after recrystallization, and under simultaneous particle fluxes (D/T/He).