Tailoring of Functionally Graded Mullite: La_2O_3 Coatings by Transferred Arc Plasma for Thermal Barrier Coatings

摘要

Mullite is the most attractive material in Material Science for TBCthermal barrier coatings. As a TBC material, enhancement in its properties like thermal shock resistance is reported when an intermittent phase like lanthanum oxideLa(2)O(3) is introduced. In this present research, effort has been put to identify La2O3 as an equivalent TBC material to ZirconiaZrO(2). A mixture of MZ (Mullite-ZrO2) and ML (Mullite-La2O3) at 10-30% weight ratio as top coat and NiCr as bond coat, is plasma sprayed on A356 aluminium specimen treated to T6 condition. The results obtained indicate that the ML2 plasma sprayed coatings exhibit regularly formed grain structure that increases the fracture toughness. The average hardness value and average adhesion strength values of the ML coatings were are 13.3GPa and 9.5MPa, which was 1.6 and 1.2times larger than the traditional Zirconia coatings. The ML coatings also showed no corrosion or spallation or crack formation after 100h of NACL salt spray test and after 100 cycles of thermal shock load at 550 degrees C at a cycle time of 10min.