Publication: Investigation on mechanical and physical properties: a study on vickers hardness, density, and porosity of alumina through the addition of tungsten trioxide
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Date
2025-09-17
Authors
Ibrahim, Maina
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Abstract
Alumina (Al2O3) cutting tools are widely used in high-speed machining mainly because of their intrinsic properties, high hardness, high melting point, and wear resistance; however, the cutting tool often fails when encountering hard material due to its inherent brittleness. Tungsten trioxide (WO₃) is a dense, thermally stable oxide that serves as a hard dispersoid and effective sintering aid in Al₂O₃ matrices. The influence of WO3 addition (0-1 wt.%), on the microstructure, phase formation, and mechanical properties of alumina (Al2O3) was investigated. The Design of Experiment (DOE) is utilized through Response Surface Methodology (RSM), including Central Composite Design (CCD), to optimize two variables among WO3 additions and sintering heating rate. The sintering temperature is fixed at 1600 ℃. The study was designed with target
values of approximately 3.9 g/cm³ density, 1600 HV hardness, and porosity below 1%, which are desirable for high-performance Al₂O₃ ceramics. The optimized variables resulted in achieving the desired responses for the hardness, density, and porosity of
Al2O3 ceramics. Empirical models are found for responses, and their quality is checked using Analysis of Variance (ANOVA) and other parameters. The microstructure, phase formation, density, and hardness properties were characterized through a field emission
scanning electron microscope (FESEM), X-ray diffraction (XRD), Archimedes' principle, and Vickers indentation technique, respectively. Although the incorporation of WO3 into the alumina matrix was intended to improve the composite’s mechanical and physical properties, the experimental results revealed a decrease in hardness and density, from 1386.7HV at 0 wt.% to 415.2 HV at 1.0 wt.%, and density from 3.83g/cm3 to 3.01g/cm3, accompanied by an increase in porosity from 0.26 to 18.21. This suggests that the addition of WO3 may have disrupted particle packing efficiency and hindered densification during sintering, leading to weaker interparticle bonding and a less compact microstructure.