Mogućnosti primene atmosferskog plazma-sprej postupka za dobijanje prevlaka hidroksiapatita na uzorcima od nerđajućeg čelika

Abstract

Hidroksiapatitna (HAp) prevlaka je atmosferskim (APS) plazma-sprej postupkom naneta na metalne uzorke napravljene od 316LVM čelika, namenjenog za izradu implantata u ortopedskoj hirurgiji. Razvoj savremenih ortopedskih implantata podrazumeva da se na podlogu od bioinertnih legura nanosi bioaktivna HAp prevlaka. Sintetički HAp je hemijski sličan onom koji čini mineralnu građu kostiju i zuba. Zahvaljujući dobrim bioaktivnim svojstvima hidroksiapatitnih prevlaka moguće je obrazovanje stabilne veze između koštanog tkiva i implantata. U radu je prikazana mogućnost primene APS postupka za dobijanje stabilnih HAp prevlaka na uzorcima od nerđajućeg čelika 316LVM. Praćena je mikrostruktura i poroznost prevlake metodom optičke mikroskopije i skenirajuće elektronske mikroskopije. Ca/P odnos je određen EDS analizom.

For decades, the standard metallic materials for hip implants, besides the 316LVM stainless steel, were titanium- and cobalt/chromium-based alloys. Although bioinert, due to their corrosion resistance, they are not biocompatible. Contemporary surgical implants are no longer made solely from bioinert metals anymore, but with deposited bioactive hydroxyapatite (HAp) coatings. Hydroxyapatite is chemically identical with the mineral constituent of bones and teeth, which, besides its biocompatibility, provides bioactivity as well. The HAp limitations are, however, weak tensile strength and low fatigue resistance for long term loadings, if used alone. This is the reason for HAp to be deposited onto the surgical implant, and to enable its bioactivity, which means intergrowth with bones, and therefore the long-lasting and mechanical stable non-cemented prosthesis. This is important predominantly because of the need for such prostheses for younger population and a better life quality. There are several contemporary techniques that have been used for deposition of these coatings onto the metal implant. The possibilities of atmospheric plasma-spraying for obtaining stable HAp coatings on 316LVM stainless steel, ordinarily used as a standard material for hip implants production, are presented in this paper. The coatings of a commercially available hydroxyapatite powder were plasma-sprayed onto specimens of medical grade 316LVM stainless steel under various operating conditions. Optical microscopy was used for microstructure and porosity characterization, while the coating morphology and Ca/P ratio were analyzed using an SEM equipped with EDX. The coating microstructure varied from a porous to a glassy structure, depending on the operating conditions and coating thickness. Coating porosity was determined to be at the lower required limit requested for the bone-coating intergrowth possibility, but nevertheless adhesion measurements showed good results. The Ca/P ratio was determined for both as-deposited coatings and after ageing in distilled water for various time and temperature combination.