Results after grinding C45 steel

The database contains results from nanoindenter, scanning microscope and also X-ray diffractometer. To determine the residual stresses and the size of the crystallites in the ferrite grains in the grinded surface layer, the Williamson Hall analysis of the X-ray diffraction patterns was performed. XRD diffraction patterns were also used to perform a modified Williamson Hall analysis, which allowed to determine the percentage of screw and edge dislocations in the ferrite grains. The X-ray diffraction studies of the grinded surface layer were carried out using a Cu lamp emitting electromagnetic radiation with a wavelength of 0.15418 nm. The X-ray diffractometer worked with the following parameters: accelerating voltage 30 kV, operating current 50 mA, diffraction step size 0.02 °, 2θ angle range 20 ° to 90 °, counting time 5 s per step. In Origin, the diffraction peaks were fitted to the calculated Gaussian function using the nonlinear least-squares method.
To determine the dislocation density, the nanoindentation method was chosen because it allows the dislocation density to be calculated from a larger volume of material than using transmission electron microscopy observations, which give only local information about the dislocation density. A dislocations mobility was also determined in the nanoindentation test. Before starting the hardness tests, a fragment of 5 mm wide was cut from the middle part of the workpiece along the diameter, perpendicular to the grinding direction. This fragment was then cut in half and both pieces were included into a thermosetting resin. The samples for hardness tests were cut by wire electrical discharge machining. In this way, two cross-sections were obtained, on which the opposite surfaces were grinded with different depths. Then the cross-sections were ground by hand on abrasive paper with gradations from 60 to 2000. Polishing of the ground surfaces was carried out mechanically on polishing discs with the use of diamond paste. To remove the Beilby layer, the samples were etched several times with a 3.5% solution of HNO3 in ethanol and polished with less and less pressure. Nanoindentation tests were performed with a constant maximum load of Berkovitch indenter equal to 20 mN. The increasing load rate to the maximum load was 1 mN/s. After reaching the maximum load, it was held for 5 seconds. Then the indenter was unloaded for 15 seconds. The hardness tests were carried out inside ferrite grains at strain hardened zone (at a distance of 5 µm to 10 µm from the surface to be ground). To minimize measurement errors, tests were performed in a room with a constant temperature of 21 °C ± 0.5 °C.
The microstructure of the surface layer after grinding was examined using a JOEL 7800F scanning microscope.