A Study on the Influence of Plasma Deposited HA and TiO2 Coatings on Fatigue Lives of Low-Carbon Steel Specimens with Respect to Various Powder in-Flight Properties

A study of the influence of plasma sprayed coatings on the fatigue lives of coated specimens was carried out. Hydroxyapatite and TiO2 coatings were deposited under three different spraying conditions onto special dog-bone shaped specimens. Average temperatures and velocities of the powders particles were measured utilizing SprayWatch fast-shutter CCD system during the deposition process. The coated specimens were then subjected to mechanical cyclical bend loading (cantilever beam) with constant deflection and the total number of cycles until stipulated specimen damage level was recorded. The influence of coatings produced under different spraying combinations on the fatigue lives of the specimens were evaluated with respect to non-coated specimens and the measured in-flight characteristics. It was found the coatings deposited under parameters resulting in high in-flight temperature and velocity of the particles substantially increase the fatigue lives of the coated specimens (up to 46% as compared to grit-blasted only specimens) while the effect on the fatigue live decreases with decreasing in-flight properties of the sprayed powders.