A influência da camada nitretada no aço AISI H13 sob efeito da fadiga térmica

Abstract

This work analyzed the thermal fatigue resistance of the plasma nitrided AISI H13 steel by monitoring the evolution of the nitrided layer and microhardness (mechanical properties). The changes in the nitrided layer were observed by means of X - ray diffraction analysis in which the formation of oxides and nitrites was observed, allowing a reduction of the defects caused by the thermal fatigue process. In spite of the occurrence of a reduction in the hardness of the material due to the thermal fatigue process, it was verified by microhardness analysis that, in the nitrided condition, the samples presented final hardness well above their non-nitrided condition. The X - ray diffraction analyzes were performed to identify the phases present in the material in the region that suffered the effect of thermal fatigue before and after the tests. Optical microscopy (OM) was used to verify the nucleation sites of the thermal cracks, which were observed from samples of 50 to 200 cycles in the non-nitrided and nitrided conditions, and the degradation of the material occurred more intensely in the non- nitrided condition. On the other hand, in the nitrided condition the material underwent only microstructural changes due to the absorption of the cyclic variations by the nitrided layer due to the iron and titanium oxides that were formed serving as thermal barrier.