Polycrystalline TZM alloy samples have been irradiated at room temperature with helium ions of energy from 75–350 keV in high vacuum. Irradiation parameters such as ion energy, total dose, and ion flux were varied, and the surfaces were examined in a scanning electron microscope. The critical dose for blister formation was found to lie between 4 and 7×1017ions cm−2and is independent of the beam flux in the range 6.7×1013–2×1015ions cm−2 s−1. However, within this flux range the average blister diameter increases with the flux and the blister number density, and the exfoliation maximizes at an intermediate flux. Blister‐cover thickness for TZM is found to be less than that for molybdenum, although the average blister diameter for the two materials differs only at the highest energy used. When the TZM surface is successively bombarded with varying ion energies, blistering is reduced compared to monoenergetic helium bombardment, but this reduction is not as substantial as for pure molybdenum.