ZrO2-3 mol% Y2O3-coated AISI 310 stainless steel was nitrided using a plasma produced by dc pulsed discharge in a mixture of N-2 and H-2 at an equilibrium temperature of 450 degreesC. The phase structure and surface morphology were investigated by X-ray diffractometry and atomic force microscopy, respectively. Glow discharge optical emission spectrometry was used to measure the depth composition of samples. The mechanical properties were studied by means ultramicrohardness indentation tests. Nitrogen atoms enter in the zirconia substituting to the oxygen atoms in the network. However, the nitrogen content measured in zirconia coating is greater than the allowed maximum content of nitrogen in doped-zirconia solid solution. The ion-nitriding process alters the surface topography of the zirconia coatings. The nitruration improves the mechanical responses of the ZrO2-3 mol% Y2O3-coated AISI 310 stainless steel. (C) 2004 Elsevier B.V. All rights reserved.