Influence of deposition temperature on mechanical properties of plasma-sprayed hydroxyapatite coating on titanium alloy with ZrO{sub}2 intermediate layer

摘要

Hydroxyapatite coatings were plasma sprayed on the Ti6AI4V substrate with and without an intermediate ZrO{sub}2 layer; meanwhile the temperatures of substrates were varied at 90, 140, and 200 ℃. The coatings were subjected to the standard adhesion test per ASTM C633-79. The purpose of the investigation was to study the effects of those processing variables on the bonding strength and failure behavior of the system. It is found that the bonding strengths of HA/ZrO{sub}2 and HA coatings generally decrease with increasing substrate temperature, except for the HA/ZrO{sub}2 coating deposited at 200 ℃. The rationale of the results is attributed to the residual stress reported in the literature. Introducing ZrO{sub}2 bond coat is found to significantly promote the bonding strength of HA coating. The possible strengthening mechanism is the rougher surface of ZrO{sub}2 bond coat and the higher toughness of ZrO{sub}2, which provide the mechanical strengthening effects. The slightly denser HA in 200 ℃ deposited HA coating cannot explain the high bonding strength of the HA/ZrO{sub}2 coating, nor the mechanical strengthening effect of ZrO{sub}2 intermediate layer should apply. It is believed that a stronger diffusion bonding is formed at the interface of HA and ZrO{sub}2, which increases the bonding between them chemically. The bonding strengths of HA/ZrO{sub}2 and HA coatings are correlated with the area fraction of adhesive failure of the coatings. The correlation explains the findings in this study.