Evaluation of niobium carbide coatings on AISI M2 and AISI H13 steels produced by thermoreactive deposition

In this work, AISl M-2 and AISl H-13 steels were treated at 1000 degrees C in molten borax containing dissolved ferroniobium and aluminium. Durations of treatment were 4 and 9 h for AISl H-13 steel and 4 h for AISl M-2 steel. Samples were characterised by optical microscopy, scanning electron microscopy (SEM), X-ray diffraction, microabrasive wear test and Vickers microhardness. Well defined layers were obtained with excellent thickness regularity. AISl H-13 steel revealed layers that measured 6.2 mu m for treatment lasting 4 h and 10.0 mu m for treatment lasting 9 h. The AISl M-2 steel was treated for 4 h, and the layer thickness obtained measured 9.0 mu m. SEM with energy dispersive X-ray spectrometry results showed a predominance of niobium and absence of iron in the layers on both types of steel. These layers consisted of niobium carbide according to X-ray analyses, and its microhardness values were about 2300 HV.