Difference in the Effect of Cold Working and Tempering on Microstructure of Mod.9Cr–1Mo Steel

The difference in the effect of cold working and tempering on the microstructure of Mod.9Cr-1Mo steel was investigated by means of X-ray diffraction (XRD), electron channeling contrast image (ECCI) and electron backscatter diffraction (EBSD) technique. For simulating the cold working, interrupted tensile tests were conducted at room temperature to prepare some specimens with 0-20% strain. Tempering was conducted at 700-760 degrees C for 0.25-6 h in order to make heat-treated specimens with the same hardness level as interrupted tensile specimens. XRD was carried out to evaluate dislocation density. ECCI and EBSD technique were employed to evaluate lath width, inter-particle spacing and high-angle grain boundary spacing such as block and packet boundary, respectively. In the pre-strained and the tempered materials, lath width, inter-particle spacing and dislocation spacing are different despite almost the same hardness. It was found that the dislocation substructure is completely different in the pre-strained and the tempered materials.