Within this project we intend to investigate the transient as well as steady state behavior of the erosion of Tungsten (W), Beryllium (Be) under seeding gas impurity ion (N, Ne, Ar) impact. For these laboratory experiments a quartz crystal microbalance (QCM) technique will be used. Experiments for W will be conducted in Vienna, while experiments for Be are foreseen in Jülich. We will study the deposition-erosion balance during interaction of energetic ionic species. The bombardment of Be and W with ionic N species leads to the formation of nitride layers. The dynamic build-up as well as the steady state erosion of such a mixed material can be quantitatively followed by our QCM setup.