Application of a fast X-ray diffraction method for studies of high temperature corrosion of steel surfaces

Summary

A fast X-ray diffraction method was applied in order to study in situ high temperature corrosion of steel surfaces. The measuring system for high temperature corrosion testing consists of an X-ray diffractometer, a high temperature device with programmable temperature controller and a Si(Li)-detector for measurements of energy dispersive diffraction spectra at temperatures from 20 to 1500°C. With a measuring time of 100 s per diffraction pattern a series of 300 measurements can be performed during one day. The atmosphere in the high temperature device can be controlled. The samples were heated in air at ambient pressure, recording X-ray diffraction spectra every 20°C. In addition, isothermal experiments were carried out at different temperatures. From the diffraction spectra the peak intensities, lattice plane distances and lattice parameters of the base material and the oxides were calculated as a function of temperature or time. The method allows an in situ identification of the corrosion products and a direct observation of phase transitions.