Effects of Gas Nitriding Temperature on the Surface Properties of a High Manganese TWIP Steel

Abstract

Abstract:The effects of gas nitriding temperature on the cross section morphology, element nitrogen distribution, and surface layer compositions of a cold rolled and pre-strained high manganese austenitic TWIP steel 25Mn-3Cr-3Al-0.3C-0.01N and the corresponding anti-corrosion ability have been studied. The results show that, depending on nitriding temperature, the distribution of element nitrogen and main phase compositions are significantly different in the nitriding layers. At a temperature lower than 500 • C, the main composition in the modified layer is S-phase and the nitrogen concentration linearly decreases from the surface to the center, while Fe 4 N forms with S-phase and a step-like distribution of nitrogen content is present at nitriding temperature of 600 • C. Caused by the increasing of modified layer thickness and the formation of S-phase and Fe 4 N, the surface hardness was obviously enhanced. Anodic polarization curves in 3.5 wt. % NaCl solution indicate that the nitrided processes have a tremendous modification effect on anti-corrosion ability. Moreover, the increase of (111) oriented grain, caused by the elevated nitriding temperature, has a positive effect on the corrosion resistance.

An Experimental Study of Temperature Effect on Properties of Nitride Layers on X37CrMoV51 Tool Steel Used in Extrusion Aluminium Industry

“…It was also described that the precipitation of CrN or Cr in complex nitride precipitations at 500 • C removed Cr from the solid solution and adversely affected the oxidation performance at this temperature [35]. Formation of CrN and γ -Fe 4 N, causes the corrosion resistance of the nitrided layer to decrease [36]. The nitrogen atoms occupy similar types of surface sites as the oxygen atoms [37] Displacement of N atoms from the surface into the bulk by interaction with gaseous O 2 will be energetically rather favourable.…”

A study on the effect of ultrashort pulsed laser texturing on the microstructure and properties of metastable S phase layer formed on AISI 316L surfaces

“…In stainless steel, the corrosion resistance is obtained through the formation of the continuous passive chromium oxide (Cr2O3) film [45,46]. When the distribution chromium becomes inhomogeneous and in some local areas its content is below the minimum value required for stainlessness, like it does within adjacent areas to chromium nitrides, it leads to the breakdown of the protective layer, which subsequently causes the deterioration of the corrosion resistance [21,27,47]. This has been supported by the electrochemical test results shown in Figure 10-14 & Table 3-4.…”

An Experimental Study of Temperature Effect on Properties of Nitride Layers on X37CrMoV51 Tool Steel Used in Extrusion Aluminium Industry

“…It was also described that the precipitation of CrN or Cr in complex nitride precipitations at 500 • C removed Cr from the solid solution and adversely affected the oxidation performance at this temperature [35]. Formation of CrN and γ 0 -Fe 4 N, causes the corrosion resistance of the nitrided layer to decrease [36]. The nitrogen atoms occupy similar types of surface sites as the oxygen atoms [37] Displacement of N atoms from the surface into the bulk by interaction with gaseous O 2 will be energetically rather favourable.…”