Characterization of cementite films prepared by electron-shower-assisted PVD method

It is important to understand the mechanical properties of single phase cementite in order to design the microstructure of advanced steels. Several papers have been published on mechanical properties of cementite embedded in steels or extracted from steels by electrolysis. However, single phase cementite is not documented. The purpose of this study is to prepare cementite films by the PVD method and to characterize their properties. We applied the electron-shower-assisted PVD method in order to produce a single phase cementite film (2.5 μm in thickness) in a C₂H₂ atmosphere at 523 K. The composition of the film was determined to be 70Fe-28C-2O (at.%). ESCA spectra indicated that the film was not contaminated with other metallic elements. The grain size of the film was revealed to be about 50 nm by AFM. The Vickers hardness was 1230 (under a load of 2.5 g) at room temperature, nearly equal to the value of 1270 of the cementite extracted from carbon steel by electrolysis. Temperature dependence of the hardness was measured up to 673 K. Young's modulus and Poisson's ratio at room temperature were 160 GPa and 0.26, respectively.