Heat treatments have been conducted at 1650℃ for 2 hours in Y-TZPstabilised with 2.5/100 molar of yttria in two differentenvironments: in air and in nitrogen gas with the specimens embeddedin a zirconium nitride powder bed. Relevant microstructural changeswere induced by these heat treatments. It is highlighted theformation of a nitrided surface layer of about 400 μm in thickness.Such layer has clear microstructural differences with respect to thebulk, and is formed by different sublayers with cubic and tetragonalphases with distinct degrees of transformability, as revealed by XRDand Raman spectroscopy. The fracture toughness and the hardness ofthe nitrided surface layer are higher than for the original Y-TZP.
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