Mathod and Performance of Blackening Mild Steel with Water Vapor in Nitrogen Environment

The reaction of water vapor and mild steel protected by nitrogen was introduced.Espetially the influence of temperature on the performance of the black film produced was studied.Via the elementary test of the samples treated at different temperatures,the relationship figures of temperature,thickness and mechanical properties of the blackening film was worked out,and the proper reaction temperature was gained.Utilizing the formula of Debye-Scherer,combining with the data of the XRD electron-diffraction,the grain size was estimated to be 27~39 nm.SEM figures revealed that the film was dense structure with less pinhole and uniform grain size,and validated the calculation result of XRD directly.