Nitriding of martensitic steel after laser melting deposition

In this study martensitic steel Fe-13% Cr-2% Ni-0.25% C in three initial state was nitrided. The steel in the initial state was made by laser melting deposition (LMD), LMD and tempering and quenching and tempering. The structure of steel after LMD was martensitic and sorbit after LMD and tempering and quenching and tempering. The result of research showed that the nitrided layer of steel after LMD is 160 μm, which exceeds the thickness of the nitrided layer of the steel after quenching and tempering by approximately 2 times. In steel after LMD and tempering, the thickness of the nitrided layer is 140 μm. The microhardness of nitrided layers of steel in all three initial state is HV 0.1 900-1000 due to the formation of Fe₄N and CrN nitrides. The drop in microhardness over the thickness of the nitrided layer of steel after LMD occurs more smoothly than that of steel after the quenching and tempering, and the thickness of its transition zone is 80 μm against 20 μm in steel after quenching and tempering. (paper)