Robert A. Poggie

Three-body abrasive wear behaviour of orthopaedic implant bearing surfaces from titanium debris

The abrasive wear behaviour of several orthopaedic bearing materials was characterized for fully conformal, reciprocating sliding contact against ultra-high molecular weight polyethylene (UHMWPE). The bearing surfaces investigated were nitrogen ion implanted Ti−6Al−4V, TiN coated Ti−6Al−4V, Ti−6Al−4V, F-799 Co−Cr−Mo, yttria-stabilized zirconia and a Zr−2.5Nb alloy with a zirconia ceramic surface. The third-body debris was introduced as either Ti−6Al−4V particles or oxidized titanium powder (black debris). The wear tests were performed in deionized water with the third-body debris entrapped between the UHMWPE and the hard bearing surface. Surface profilometry measurements, scanning electron microscopy (SEM) and optical microscopy showed the severity of damage to the hard bearing surfaces to increase with decreasing hardness. The abrasion damage to the UHMWPE increased as the roughness of the opposing, hard bearing surface increased. Surface profilometry and energy dispersive spectroscopy (EDS) also showed oxidized titanium (black debris) to form an adherent transfer layer on all of the hard bearing surfaces. Nitrogen ion implantation of Ti−6Al−4V was ineffective in reducing wear of both the Ti−6Al−4V substrate and the UHMWPE. Solid yttria-stabilized zirconia and zirconia-coated Zr−2.5Nb showed no evidence of abrasion damage and produced the least amount of UHMWPE wear. These results are attributed to the high hardness and excellent wear resistance of zirconia and the excellent wettability of ZrO2 due to its relatively high ionic character in comparison to metals and covalently bonded compounds.

The effects of surface oxidation and segregation on the adhesional wear behavior of aluminum—bronze alloys

The worn surfaces of selected Cu-A1 alloys, resulting from sliding contact with a sapphire right cylinder, along with unworn surfaces and wear debris, were characterized using an appropriate combination of scanning electron microscopy (SEM), optical stereomicroscopy, X-ray diffraction (XRD), and X-ray photoelectmn spectroscopy (XPS). XPS, angle-resolved XPS (ARXPS) and ion sputter profiling techniques were employed to characterize surface compositional changes occurring in the unworn and worn surfaces as a function of increasing aluminum content. The transfer of Cu—A1 alloy to the sapphire counterface (adhesional wear of the Al-bronze) increased with increasing aluminum content, which corresponded to increased wear and damage to the alloy surfaces. XPS and SEM analyses of pure copper and a Cu-1 weight percent (w/o) A1 alloy showed the worn surfaces to consist of a smooth and continuous Cu2O layer. ARXPS analysis of as-polished and worn surfaces of Cu-4 w/o A1 and Cu-6 w/o A1 alloys showed significant surf...