URL https://www.researchgate.net/profile/Naoyuki-Sano/publication/305717877/figure/fig1/AS:415503391707146@1476075137038/Optical-micrographs-of-the-cross-sections-of-the-nitrocarburized-surface-in-a.png
URL2https://www.researchgate.net/figure/Optical-micrographs-of-the-cross-sections-of-the-nitrocarburized-surface-in-a_fig1_305717877
