Development of plasma nitrocarburizing and post-oxidation technology for the replacement of Cr6+ flating for application to vehicle engine shafts

作者：Lee Insup^*

来源：Metals and Materials International, 2008, 14(1): 77-81.

DOI：10.3365/met.mat.2008.02.077

• plasma nitrocarburizing
• post oxidation
• epsilon-Fe2-3(N,C)
• Cr6+ plating
• Fe3O4

Plasma nitrocarburizing and post-oxidation treatments were performed to improve the wear and corrosion resistance of S45C steel. Plasma nitrocarburizing was conducted for 3 h at 570 degrees C in a nitrogen, hydrogen and methane atmosphere to produce the epsilon-Fe2-3(N,C) phase. It was found that the compound layer produced by plasma nitrocarburising was predominantly composed of the c-phase with traces of the gamma'-Fe-4(N,C) phase. The thickness of the compound layer was approximately 12 pm and the diffusion layer was approximately 300 pin in thickness. Plasma post oxidation was performed on nitrocarburized samples with various oxygen / hydrogen ratios at a constant temperature of 500 degrees C for 1 h. The very thin magnetite (Fe3O4) layer 1 mu m to 2 pin in thickness on top of the compound layer was obtained by plasma post oxidation. It was also confirmed that further improvement of the corrosion characteristics of the nitrocarburized compound layer was possible with an application of the superficial magnetite layer. Finally, throttle valve shafts of S45C steel were treated under Optimum plasma processing conditions. Accelerated life time test results using a throttle body assembled with a shaft treated by plasma nitrocarburising and post oxidation showed that plasma nitrocarburizing and plasma post-oxidation processes could be a viable technology in the very near future in place of Cr6+ plating.

• 出版日期2008-2