Evaluation of erosion and fatigue resistance of ion plated chromium nitride applied to turbine blades

Abstract

High temperature oxidation and erosion resistant ceramic coating materials have been recently used for turbine rotor blades under high temperature dry steam conditions. It is, therefore, important to evaluate not only the physical or mechanical properties but also characteristics of erosion and fatigue of such materials for purposes of material selection and to predict the working life of plants. Ion plated CrN samples with a sublayer of plasma nitride on martensitic stainless steel were prepared. Dynamic hardness, in a high temperature environment of 723 K, was obtained by the impact of a glass ball. Fatigue tests of the CrN coating materials were conducted at 723 K, the same temperature as is typically used in the environment of turbine rotor blades, and the results were compared with fatigue resistance at room temperature. Erosion tests by the impact of SiO 2 particles with a mean diameter of 326 μm at an impact velocity of 104 m s −1 were performed at room temperature to evaluate the fundamental erosion resistance, and the dependence of impact angle on erosion damage of CrN coating materials was compared with the resistance of an alumina bulk material. Consequently, the erosion rates at room temperature and the dynamic hardness distributions of the CrN coating materials at 723 K indicated that the materials used in this study had excellent erosion resistance and the fatigue tests for the coating materials indicated the possibility of applications to actual turbine blades that are used at 723 K.