Tribological hard layer synthesis by duplex ion beam treatment

Two different modified ion beam processes have been performed to overcome the thickness limitation and the corresponding hardening effect in conventional ion beam processing. One of the processes is the preliminary ion irradiation with high energy of 40 keV followed by low energy (300 eV) nitrogen irradiation of high flux density (10 mA/cm(2)) or vice versa onto mold and tool steels. The maximum hardened layer thickness could be obtained to be more than 20 mu m. Hardness was enhanced by 1.5 to 2.2 times depending on material as well as process conditions, and thereby highly improving wear resistance which was comparable to that of plasma nitrided steels. The other process was the synthesis of oxide layer through ion irradiation under oxygen partial pressure at various elevated temperatures in Zircaloy. The process well produced almost stoichiometric ZrO2 layer of an order of mu m thickness within a few tens minutes. In addition oxygen penetration of about 20 mu m could be obtained with process control. The oxide layer formation and the deep penetration of oxygen effectively enhanced the surface hardness as well as wear resistance. The overall processes and corresponding structural and property changes are discussed.