Surface modification of ZrO2-3Y2O3 ceramics with continuous Ar+ ion beams

Abstract

Microindentation and nanoindentation methods have been used to study the changes in microhardness, nanohardness and elastic modulus of partially stabilized zirconia ceramics before and after its treatment with a continuous Ar+ ion beam. The accelerating voltage was 30 kV. The experiments were performed at current densities (j) of 300 and 500 μA/cm2. The fluence was 1016–1018 cm−2. It is shown that Ar+ ion beam treatment increases the strength of the near-surface layers at a depth exceeding the penetration depth of accelerated ions by an order of magnitude or more. This indicates a long-range effect, which has been discovered earlier during ion beam treatment of metals and alloys. Treatment with ion current density of 300 μA/cm2 at a fluence of 1.1 × 1017 and 5 × 1017 cm−2 maximally increases microhardness and nanohardness (by 14%), and elastic modulus (by 20%). The phase composition of ceramics was studied using the XRD analysis. Additionally, ceramic samples were studied using the methods of Raman scattering and pulsed cathodoluminescence. The XRD analysis indicated that Ar+ ion beam treatment changes the phase composition of the near-surface layer several micrometers deep. The analysis of structural changes in the surface layers showed that continuous Ar+ ion beam treatment results in surface recrystallization, and it is not followed by negative processes, such as melting, cracking and erosion, observed during treatment by high-intensity pulsed ion beams. Shock-wave mechanisms of ceramic layer hardening and those related to accumulation of high static stresses and generation of dislocations are discussed.