Statistical evaluation of microhardness in B₄C ceramics doped with different CoCrFeNiMo HEA concentrations

Abstract

This study presents a statistical analysis of the microhardness behaviour of B₄C ceramics doped with different concentrations of CoCrFeNiMo high-entropy alloy (HEA), with the objective of understanding how the metallic reinforcement influences densification, indentation response and microstructural homogeneity. All samples were consolidated using Spark Plasma Sintering under identical processing parameters to isolate the effect of HEA content. Microstructural observations revealed notable differences in particle distribution, porosity levels and contrast variations associated between monolithic B4C and HEA doped samples [1]. A minimum of 45 indentations were made for Vickers microhardness measurements, performed systematically across the surface of each sample. The results were treated statistically to evaluate dispersion, confidence intervals and the relationship between metallic reinforcement and mechanical performance. Composites with moderate HEA additions exhibited higher hardness stability and narrower data distributions, suggesting improved particle bonding and reduced microstructural defects. On the other hand, higher HEA concentrations lead to higher hardness and density, even though it produced larger dispersion of results. This is probably due to the coexistence of soft metallic regions and hard ceramic domains, leading to non-uniform load distribution during indentation [2]. The statistical evaluation highlights that the optimal reinforcement level is not necessarily the highest fraction but the one that achieves the best balance between densification, hardness and microstructural uniformity. These findings contribute to understanding how HEA additions modify the mechanical response of B₄C-based composites and provide criteria for future hybrid ceramic–metal systems for advanced engineering applications.