Nitriding of Fe–18Cr–8Mn stainless steel powders by mechanical alloying method with dual nitrogen source

• Nitriding was achieved by the dissociation of chromium nitrides and nitrogen molecules.
• Structure with fine chromium nitrides particles distributed on the Fe matrix was formed.
• Austenitization occurred during the processing.
• Samples with a fully austenite structure were obtained after sintering.
• The microhardness values of samples were higher than the standard 316 stainless steel.

In the present work, mechanical alloying (MA) method was applied to nitride Fe–18Cr–8Mn stainless steel powders through simultaneous dissociation of chromium nitrides and nitrogen molecules at room temperature. The formation of nitriding originated in the combined effects of the introduction of mechanical energy, plastic deformation, and refinement of particle and grain. The nitrogen content reached to 3.69% after milling for 30 h. The microstructure features of powder particles were affected by the milling time. The phase transformation of α-Fe to γ-Fe phase occurred after milling for 15 h, which was resulted from the function of nitrogen solution and the MA process. The crystalline size decreased, while the internal strain increased by increasing the milling time. The sintering process performed in nitrogen atmosphere could prevent massive nitrogen loss. The samples with powder milled for 30 h developed a fully austenite structure after sintering and subsequent water quenching, which had 3.51% of nitrogen content, 92% of relative density and the microhardness reached to 549 HV0.1.

Figure optionsDownload as PowerPoint slide