AlNbO4-Al2 O3-NbOx Composite Coating Prepared by Reactive Plasma Spraying

The work aims to study microstructure, mechanical properties as well as friction and wear properties of AlN-bO4-Al2O3-NbOx composite coating prepared by plasma spraying in Al-Nb2O5 thermit system. A composite ceramic coating containing AlNbO4, Al2O3 and NbOx was fabricated by plasma spraying self-made Al-Nb2O5 composite powder prepared by spray granulation with Nb2O5 and Al powders. Structure and phase composition of the composite coating were tested and analyzed with a scanning electron microscope (SEM), energy dispersive analyzing system (EDS) and X-ray diffractometer (XRD), microhardness with a microhardness tester and crack extension force (Gc) in hardness indentation method. The friction and wear properties of the unlubricated coatings were tested with pin-disc-type abrasion tester. The XRD analysis showed that the composite coating consisted of AlNbO4, Al2O3 and NbOx phases. The SEM results showed that the coating had an alternatively distributed lamellar structure. In the range of 28~32 kW, hardness of the coating increased with the increase of spraying power and was up to 912HV0.1 at 32 kW; crack extension force of the coating increased firstly then decreased and the maximum was 14.14 J/m2 at 30 kW; the friction coefficient decreased firstly and then remained constant with the increase of power; the friction coefficient was 0.7~0.8 at 28 kW, and 0.5~0.6 at 30 kW and 32 kW; the wear volume decreased firstly and then increased, and amounted to the minimum at 30 kW. Obvious furrow, groove and peeling-off were observed on the worn sample. The composite coatings have an alternatively distributed multiphase lamellar structure consisting of AlNbO4, Al2O3 and NbOx. Performance of the composite coating is the best at the spraying power of 30 kW. Main wear mechanisms of the composite coating are abrasive wear and fatigue wear. © 2017, Chongqing Wujiu Periodicals Press. All rights reserved.