Fig. 3. CEMS spectra from(a) the surface layer (region①), (b) the layer exposed after the removal of 22 μm (region②), (c) the layer at 65 μm depth (region③), and (d) bulk of AISI H13 steel. The phases identified in (a) are ε-Fe2–3N, nitrogen martensite α′-Fe(N), iron oxy-nitride FeON, and magnetite Fe3O4 ; in (b) and (c) carbon martensite α′-Fe(C) and nitrogen martensite α′-Fe(N) plus vestigial austenite γ-Fe in (b), and in (d) only carbon-martensite α′-Fe(C). The white double arrow in the upper right corner of each spectrum indicates 1% effect.