Medida de porosidade em compósitos B4C-Nb por meio de análise e processamento digital de imagem

Abstract

Constant research efforts have been conducted in materials selection to combine and improve the properties of interest, service life and production cost. In this context, boron carbide (B4C) stands out for having a high mechanical performance, being the material that has the fourth highest hardness (> 29.1GPa) among ceramic materials. However, porosity is seen as a limiting factor for the high performance of this group of materials, to which boron carbide is found. Porosity control is usually conducted through imprecise techniques, and indirect or costly measures for quantification. This work quantified the porosity of boron-niobium carbide (B4C -Nb) composites obtained from high pressure - high temperature (HPHT - high pressure high temperature) sintering process through analysis and digital image processing (PDI) by microscopy optical (MO) after surface preparation with controlled and automated parameters. The results obtained were compared with those obtained using the mercury intrusion porosimetry method. The semi-quantitative chemical characterization of the composites was performed using the Energy Dispersive Spectroscopy (EDS) technique. Mercury intrusion indicated that there is a descending order for pores in the groups containing 2, 5, 10 and 20% Nb, unlike the descending order for porosity that was found by the manual PDI technique, which had the sequence 10, 20, 5 and 2% Nb. These differences in results can be attributed to heterogeneities in the presence of pores between sintered and analyzed from the same groups and inaccuracies in the mercury intrusion technique.