Hardness, friction, and structure of ion beam-modified titanium alloys, magnesia, and zirconia.

摘要

This work is concerned with metals and ceramics--titanium, stainless steel, magnesia, and zirconia--that have good bulk properties. The objective of the research is to further improve their mechanical properties by changing the surface structure and/or composition through ion implantation. The focus is on how ion beam modification affects hardness, friction, toughness, and wear to determine the extent of possible changes and to understand their source.; Titanium was modified by ion beam mixing gold into the surface to improve corrosion resistance. Friction, corrosion, and structure were studied as a function of composition. Some amorphous material was observed with transmission electron microscopy over the composition range of 15%-60% Au. Higher Au content showed an extended solid solution. Corrosion resistance was greatly improved for 40% Au or more. Pin-on-disk friction was generally higher with the added Au, but was lowest with a composition slightly gold-rich of pure titanium.; Previous work on steel showed significant friction improvements after mixing in titanium and iron and then implanting carbon and nitrogen. By using energy dispersive spectroscopy (EDS) line profiles in conjunction with scanning electron microscopy (SEM) and Alpha Step profilometry it was possible to distinguish deformation of the surface from material removal. This showed that the modified layer stays intact while it is deformed into the substrate.; Single crystal MgO implanted with Xe showed an increase in hardness with dose. TEM showed a dense array of fine damage at low doses. Higher fluences produced textured polycrystalline material and Xe inclusions, some of which were solid and aligned with the MgO lattice.; Single crystal cubic zirconia implanted with Ne, Ar, or Xe showed that the implantation damage, not the dose, relates to hardness changes. All ions caused a 15% increase in hardness followed by a 15% decrease in hardness with increased damage energy. Deep implants showed hardness and toughness increases of 50%. The friction coefficient for the softer samples remained at a stable, low value for 10,000 cycles and caused less ball debris than unimplanted or low dose implants. Both channeling and TEM analysis show a significant amount of oriented single crystalline material remains even up to doses of 1 {dollar}times{dollar} 10{dollar}sp{lcub}17{rcub}{dollar} Xe/cm{dollar}sp2{dollar}. Additionally, solid and fluid Xe is observed in the diffraction pattern as well as some recrystallized zirconia.