Open AccessInfluences of Laser Remelting on Microstructure and Thermal Shock Resistance of Al2O3-13wt.%TiO2 Coatings Deposited by Plasma Spraying
Author(s) -
Dongsheng Wang
Publication year - 2019
Publication title -
iop conference series. materials science and engineering
Language(s) - English
Resource type - Journals
eISSN - 1757-899X
pISSN - 1757-8981
DOI - 10.1088/1757-899x/585/1/012021
Subject(s) - materials science , thermal shock , microstructure , coating , ceramic , lamellar structure , composite material , thermal spraying , shock (circulatory) , plasma , thermal barrier coating , phase (matter) , laser , scanning electron microscope , metallurgy , optics , medicine , chemistry , physics , organic chemistry , quantum mechanics
Al 2 O 3 -13wt.%TiO 2 composite ceramic coatings were prepared by plasma spraying and laser remelting. Morphology, microstructure and phase composition were analyzed by scanning electron microscope (SEM) and X-ray diffractometer (XRD). Meanwhile, effects of laser remelting on thermal shock resistance of plasma-sprayed coatings were investigated and the thermal shock failure mechanism of coatings were discussed. Results demonstrate that after laser remelting, particles on the ceramic coating are refined and the lamellar structure disappears, thus increasing density and getting a remelting coating basically without defects like cracks. Laser remelting metastable phase γ-Al 2 O 3 is transformed into a stable phase α-Al 2 O 3 . Due to low heat conductivity coefficient of ceramic materials, it is impossible to remelt the whole ceramic coating at laser remelting. An isometric crystal remelted zone with small grains, a sintered zone and a lamellar remained plasma-sprayed zone are formed on the remelting ceramic coating. Compared with plasma-sprayed coating, the laser-remelted coating has better thermal shock resistance. The thermal shock failure form of ceramic coating deposited by plasma spraying is basically corner peeling, while the thermal shock failure forms of laser-remelted ceramic coating includes both corner peeling and considerable local peelings in the center. Influences of laser remelting on thermal shock resistance of coating are mainly manifested as reduced initial failure resistance of coatings, decelerated crack propagation on coatings and changing failure mode of coatings.