Improvement of surface properties by modification and alloying with high-power ion beams

Surface treatment and alloying experiments with Al, Fe, and Ti-based metals as well as Si wafers were conducted on the Repetitive High Energy Pulsed Power-I (RHEPP-I) accelerator [0.8 MV, 20 Ω, 80 ns full width at half maximum (FWHM) pulse width, up to 1 Hz repetition rate] at Sandia National Laboratories. Ions are generated by the magnetically confined anode plasma (MAP) gas-breakdown active anode, which can yield a number of different beam species including H, C, N, O, Kr, and Xe, depending upon the injected gas. Enhanced hardness and wear resistance have been produced by treatment of 440C stainless steel, by the mixing of a thin-film Pt coating into Ti-6Al-4V alloy, and of a Si coating into Al 6061-T6 alloy (Al-1.0Mg-0.6Si). Mixing of a thin-film Hf layer into Al 6061-T6 has improved its corrosion resistance by as much as four orders of magnitude in electrochemical testing, compared with untreated and uncoated A16061. Processing of Si was used to validate simulation codes. When treated with nitrogen ions, melt and full epitaxial growth was observed to depths of 4-6 μm. Experiments are ongoing to further understand the microstructural basis for these surface improvements.