Using a simulation code for dynamic interactions between energetic ions and solid materials, the influence of C impurity concentration on net erosion of reduced-activation ferritic/martensitic steel, RAF (Fe in the simulation), and W materials exposed to a 0.33 keV H+ and I keV C+ impurity mixed ion beam relevant to a fusion plasma boundary has been studied. A comparison of the simulation results between the Fe and W materials at C impurity concentrations less than C: 1.00% is described and discussed. In particular, emphasis is paid to a quantitative comparison between depth profiles of C impurity deposited on the materials and the experimental data, which were obtained by the H and C mixed ion beam exposure experiments of RAF (F82H in the experiment) and W materials. For the W material, chemical erosion (CH4 emission) of the deposited C impurity by the H+ impact is taken into account in the simulation. The C impurity concentration causes a significant difference in net erosion between the two materials. For the Fe material, net erosion is suppressed with increasing C impurity concentration. In contrast, for the W material, net erosion is enhanced. In the depth profile, there is also a significant difference between the two materials. At C: 0.11%, the impinging C impurity is hardly deposited on the Fe material. For the W material, the depth profile at C: 0.11% shows a local peak around a certain depth, which is in good agreement with the experimental data at 653 K. This agreement indicates no contribution of the chemical erosion in the H-C-W system, which is quite different from that in the H-C system where the chemical erosion occurs. The difference seems to indicate that the chemical erosion in the H-C-W system is dependent upon amounts of the deposited C impurity or the binary alloy phase change between W and C. When the C impurity concentration increases to C: 0.84%, the impinging C impurity is deposited on the Fe material. The depth profile shows a maximum at the top surface, which reproduces the experimental data at 453 K. For the W material, the depth profile at C: 0.84% shows almost the same tendency as that at C: 0.11%, but shows a larger amount of the deposited C impurity. The simulation result at C: 0.84% is in disagreement with the experimental result at 653 K, which shows a maximum at the top surface. This disagreement is not fully explained by only the chemical erosion.
