Lanthanum magnesium hexaluminate thermal barrier coatings with pre-implanted vertical microcracks: Thermal cycling lifetime and CMAS corrosion behaviour

Atmospheric plasma-sprayed (APS) coatings have a layered structure as well as lower strain tolerance and a shorter lifetime than EB-PVD coatings. In this study, TBCs composed of a LaMgAl11O19 (LMA) top coat and a NiCrAlY bond coat were prepared by APS coupled with dry-ice blasting to implant vertical microcracks in the top coat. The thermal cycling lifetime and CMAS corrosion behaviour of LMA-TBCs with pre-implanted vertical microcracks were investigated in detail. The results show that the LMA top coat possesses an improved proportion of vertical microcracks and that the corresponding TBC has an improved thermal cycling lifetime. The vertical microcracks in the top coats, which not only reduce the thermal stress but also improve the strain tolerance of TBCs, dramatically contribute to the improvement in the thermal cycling lifetime. Surprisingly, the CMAS corrosion resistance of LMA-type TBCs with implanted vertical microcracks is better than that of conventional TBCs with a typical layered structure.