Evaluation of the Elastic and Plastic Contact Wear Performance of Plasma and Flame Sprayed 13 and 45 wt% TiO₂ Alumina-Titania Coatings Available to Purchase

Atmospheric plasma and oxy-acetylene flame were used to spray alumina-titania micrometer sized particles with respectively 13 wt.% and 45 wt.% of TiO₂ (AT-13 and AT-45). Plasma spraying was also used to spray nanometer-sized- agglomerated particles (AT-13). The enthalpy of spray guns was varied to achieve coatings with different phases and structural characteristics. The influence of the different structural characteristics and the phases of coatings on their hardness and tribological behavior was then studied. The wear resistance was determined by dry elastic contact between an alumina ball, 6 mm in diameter, and the polished coated discs. The ball was moved at a linear speed of 0.1 m/s under a load of 5 N during 20,000 cycles. Drilling tests between a steel drill bit, 12.5 mm in diameter, and the coating surface were also carried out in order to determine the wear resistance under plastic contact. The wear test results showed that AT-13 coatings were more resistant than the AT-45 ones, which was due to the presence of α and γ alumina, phases presenting a high mechanical resistance. On the contrary the resistance of AT-45 coatings, consisting of Al₂TiO₅ and Al₆Ti₂O₁₃ brittle phases of low hardness, was poorer. Under elastic contact the reduction of the wear resistance of coatings elaborated by flame spraying was not obvious, but under plastic contact the plasma sprayed coatings were more resistant than those deposited by oxy-acetylene flame.