Processo SHTPN e seus efeitos na microestrutura e microdureza de aço IF

Abstract

Interstitial free steels (IF steels) are highly used in the automotive industry, mainly due to the high formability for sheet metal fabrication. The effect of nitrogen addition on steels have been widely studied due to the potential to improve corrosion resistance, wear resistance and mechanical strength. The differences between steels alloyed nitrogen or carbon are mainly due to differences in the electron configuration of the crystal lattice, distribution and mobility of dislocations, and the atomic distribution in the solid solution. Regarding the IF steel, the favorable characteristics of the process of adding nitrogen such material offers (reduced content of interstitial elements) demonstrated significant differences in mechanical behavior of surfaces of interstitial free steels modified by enrichment by nitrogen plasma nitriding. The new technique SHTPN (Solution Heat Treatment after Plasma Nitriding) emerges as an effective alternative compared to other widely used, mainly due to getting great results in less time processing. Thus, the present study aims to investigate the application of the technique in IF steels. Different solubilization conditions were applied to samples subjected to nitriding thermochemical treatment. Hardness and microstructure of the samples produced were evaluated and confirmed increase of hardness on the surface and just below it in the samples submitted to the technique SHTPN. The solubilization was efficient in increasing the effective layer depth, redistributing hardness achieved by nitriding. In addition, the solubility of nitrogen is sensitive to the variation of the parameters tested (time and temperature).