FABRICATION AND MICROSTRUCTURE OF ZRO2 NICRCOALY GRADED COATING BY PLASMA SPRAYING/

An 8 wt.% Y2O3-ZrO2/NiCrCoAlY graded coating was fabricated on a TC4 ( Ti-6Al-4V) surface by air plasma spraying. Microscopic analysis showed that the ZrO2/NiCrCoAlY graded coating exhibits a stepwise distributi on in composition from metallic bond layer to ceramic top layer, consi sting of t'-ZrO2 phase and supersaturated Ni-based solid solution phas e, and displays tight coherence with the TC4 substrate. In addition to mechanical combination, chemicometallurgical reaction combination occ urs at some locations and small amounts of NiTi2 and TiAl3 phases at t he coating-substrate interface develop during spraying.