Elastic and plastic behavior of plasma-sprayed hydroxyapatite coatings on a Ti-6Al-4V substrate

A novel approach that combines the indentation tests with nonlinear finite element modeling (FEM) is proposed to estimate the elastic/plastic constitu tive relation of plasma-sprayed hydroxyapatite (HA) coatings on a Ti-6Al-4V substrate. The Ramberg-Osgood constitutive equation can well describe the deformation behavior of plasma-sprayed HA coating on Ti-6Al-4V. A reasonabl e estimation for the elastic modulus of the HA coatings is given, based on the fact that the coating consists of a crystalline phase, an amorphous pha se and pores. The Ramberg-Osgood equations of the coatings indicate that th e post-treatment increases both resistance to elastic and plastic deformati on, but no effect on strain hardening behavior. The post-treatment, however , could reduce the resistance to coating/substrate separation. The influenc e of titanium substrate becomes more significant with decreasing coating th ickness and increasing indentation load because the plasma-sprayed HA coati ngs exhibit much less resistance to indentation deformation than does Ti-6A l-4V. (C) 2001 Elsevier Science Ltd. All rights reserved.