Temperature Dependence of the Hardness of Single-phase Cementite Films Prepared by An Electron-Shower PVD Method

To design advanced steel, it is important that the mechanical properties of the cementite phase are studied. However, few papers on these properties have been published. For those that have been published, the samples were cementite embedded in steels or extracted from steels by electrolysis.The purpose of this paper is to prepare a thick cementite film without the oxide, and to study the temperature dependence of the hardness in detail.A single phase cementite film, 3 μm thick, was prepared by the electron-shower PVD method. The composition of the film was Fe : C : O=76 : 24 : 0. The Vickers hardness of the cementite was 1140 at room temperature and decreased to half at 400°C. The hardness of composite film of Fe and cementite is explained by the law of mixture. The cementite film was oxidized above 400°C in atmosphere, but was very stable at room temperature.