Structural characteristics and residual stresses in oxide films produced on Ti by pulsed unipolar plasma electrolytic oxidation

Raja H.U. Khan (1) , Aleksey Yerokhin (1) , A Matthews (1)

1 Department of Materials Science and Engineering [Sheffield]

Oxide films, 7 to 10 μm thick, were produced on commercially pure titanium by plasma electrolytic oxidation in a sodium orthophosphate electrolyte using a pulsed unipolar current with frequency (ƒ) and duty cycle (δ) varied within f = 0.1 to 10 kHz and δ = 0.8 to 0.2 respectively. The coatings comprised a mixture of an amorphous phase with nanocrystalline anatase and rutile phases wherein the relative content of rutile varied from 17 to 25 wt%. Incorporation of phosphorus from the electrolyte into the coating in the form of PO2-, PO32- and PO43-, as demonstrated by EDX and FT-IR analyses, seems to contributed the formation of the amorphous phase. Residual stresses associated with the crystalline coating phase constituents were evaluated using the X-ray diffraction Sin2ψ method. It was found that, depending on the treatment parameters, internal direct and shear stresses in anatase ranged from -205 (±17) MPa to -431 (±27) MPa and from -98 (±6) MPa to -145 (±10) MPa respectively, whereas the rutile structure is comparatively stress free.

Mots clés: Physical Sciences

Raja H.U. Khan, Aleksey Yerokhin, A Matthews. Structural characteristics and residual stresses in oxide films produced on Ti by pulsed unipolar plasma electrolytic oxidation. Philosophical Magazine, 2008, 88 (06), pp.795-807. ⟨10.1080/14786430801968603⟩. ⟨hal-00513872⟩