CRATERING BEHAVIOR IN SINGLE-CRYSTALLINE AND POLYCRYSTALLINE COPPER IRRADIATED BY AN INTENSE PULSED ION-BEAM

When treated with intense pulsed ion beams (IPIB), many materials exhi bit increased wear resistance, fatigue life, and hardness. However, th is treatment often results in cratering and roughening of the surface. In this work, high purity single crystal and polycrystalline copper s amples were irradiated with pulses from an IPIB to determine whether t his cratering is due to (1) bulk alloy content, (2) impact of anode de bris, or (3) grain structure. Samples were treated with 1, 2, 5, and 1 0 shots at an average energy fluence per shot of 2 and 5 J/cm(2). Shot s were about 400 ns in duration and consisted of a mixture of carbon, hydrogen, and oxygen ions at 300 keV. It was found that the single cry stal copper cratered far less than the polycrystalline copper at the l ower energy fluence. At the higher energy fluence, cratering was repla ced by other forms of surface damage, and the single crystal copper su stained less damage at all but the largest number of shots. Molten deb ris from the Lucite anode (the ion source) was removed and redeposited on the samples with each shot. From this, we conclude that neither bu lk alloy content nor anode debris impact cause cratering. Grain struct ure affects cratering, although the mechanism for this is not determin ed in this study. (C) 1998 Elsevier Science S.A. All rights reserved.