HYDROXYAPATITE COATINGS ON TINI SHAPE-MEMORY ALLOYS

The microstructure of hydroxyapatite (HAP) ceramic coatings deposited by plasma spraying on TiNi shape memory alloy substrates was investiga ted. With respect to metal/ ceramic interface strength, excellent coat ings of HAP on TiNi substrates were prepared. From the point of view o f adherence, these coatings possess higher strength than Epoxy 1200 ad hesive (approximate to 30 MPa). The observed excellent metal/ceramic i nterface strength is attributed to the formation of chemical bonding a ccording to the reaction Ca-10(PO4)(6)(OH)(2) + 2TiO(2) --> 3Ca(3)(PO4 )(2) + CaTi2O5 + H2O and the energy dissipation due to stress-induced martensite formation (SIM) and/or martensite reorientation (RE) during stressing the composite and failure. The applied power parameters of the plasma spraying influence the porosity and fusion between particle s of the ceramic coatings.