Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

Database of physical, chemical, biological and mechanical properties of fine grained PM2000 with and without alumina scale

After a thermal oxidation (1100ºC) the alloy PM 2000 is coated in situ with an alfa-alumina layer. Important to remark that thermal oxidation, applied in the last stage, and consequent alumina scale formation, did not affect the dimensional tolerance of the investigated components.

The alumina-coated alloy presents high tensile strength (930 MPa), high elongation (24%), and elevated impact strength (250 J/cm2). In addition, the candidate alloy exhibits sufficient bending fatigue strength (fatigue limit of about 550MPa). Interesting to note that the elevated compressive residual stresses at the coating accounts for the capability of the alloy to be deformed up to about 1% without compromising the scale integrity, which is a great advantage when considering the 0.1-0.2 % elongation for bulk alumina.

Long-term wear tests in a join simulator reveal that the UHMWPE polyethylene wear of the uncoated alloy is similar to that of CoCr alloy. The worst behaviour of the alumina coated material with respect to the bulk alumina results from the higher roughness of the coating. Further investigation is needed to reduce the roughness of the alumina coated alloy to the value of 20 nm indicated in the ISO standard.

The alumina layer is fine (a few microns) but dense and tightly adherent to the substrate, which accounts for a superior in vitro corrosion resistance. Therefore, a very low ion release is expected to occur in vivo.

Cell culture tests, including primary human osteoblasts reveals an excellent biological acceptance. It has been found that osteoblasts are able to produce ALP, a specific marker of cells with bone-forming activity. In this respect, PM 2000 holds the promise to be suitable substrate for bone integration.

A data base of the PM 2000 with and without scale collecting mechanical, chemical and biological behaviour at ambient temperature would allow the identification of potential applications for medical devices.

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