A comparative study on thermally sprayed alumina based ceramic coatings

Aluminium oxide is relatively cheap material, abundant almost everywhere and therefore it is widely used for thermal spray applications. Various alumina based powder containing 13 wt. Titania, two different 40 wt.% Zirconia and three different compositions of alumina-zirconia-chromia were deposited by atmospheric plasma spraying (APS) and high power plasma spraying (HPPS). The coatings obtained were evaluated by optical microscopy, microhardness measurements, X-ray diffraction and porosity measurements. Moreover, abrasion and friction wear resistance were evaluated by using Pin-on-Disc machine. Microhardness values of APS coatings are relatively high as compared to HPPS coatings except in alumina-zirconia-chromia coatings. HPPS have higher hardness values. APS coatings are much coarser and show higher porosity values than HPPS coatings. The best wear/friction behaviour exhibited coating Al2O3-40 wt.% ZrO2 that deposited from agglomerated and sintered powder type. (C) 2000 Kluwer Academic Publishers.