Characterization and thermal shock behavior of composite ceramic coating doped with ZrO ₂ particles on TC4 by micro-arc oxidation

A kind of composite ceramic coating was prepared on the surface of Ti-6Al-4V alloy to improve its thermal shock resistance by micro-arc oxidation method in a NaAlO ₂ and NaH ₂ PO ₂ solution doped with ZrO ₂ micro-particles. Phase structure of the MAO coatings was studied by XRD techniques. The main crystal phases of the composite coating were Al ₂ TiO ₅ , rutile TiO ₂ and ZrO ₂ , no corundum phase, α-alumina and γ-alumina. SEM investigations revealed that in Al-P MAO coating a volcano top-like pore surface was exhibited, while for Al-P-Zr MAO coating only few pores and island-like melting oxidation with different sized around the volcano. The presence of doped ZrO ₂ particles was beneficial to the growth of the coatings, but not good for surface toughness. Thermal shock resistant property was tested using the home-made thermal shock testing device. The thermal shock results indicated that no cracks occurred on the surface and no peeling phenomenon happened on the interface bonding zone after 50 cycles under temperature drop of 980 °C. A thermal shock mechanism was proposed based on the microstructure and good metallurgical bond strength of membrane-based interface as well.