COMMINUTION INFLUENCE ON MECHANICAL PROPERTIES OF NbC CONSOLIDATED BY SPARK PLASMA SINTERING

Reference Presenter Authors
(Institution)
Abstract
09-045 Ana Julia Oliveira Tertuliano Tertuliano, A.J.(Universidade de São Paulo); Boidi, G.(Universidade de São Paulo); Machado, I.F.(Universidade de São Paulo); Trombini, V.(Universidade Federal do ABC); Niobium carbide is a promising material for tooling and industry applications, since it presents a high hardness, a high melting point (3610 °C), a good resistance to chemical attack and an excellent electrical conductivity. The material is usually consolidated at high temperatures with conventional techniques, causing grain growth. However, the use of Spark Plasma Sintering technique (SPS) could achieve lower holding sintering times and temperatures and consequently refine grain size. This work aims to evaluate the influence of powder comminution on NbC mechanical properties sintered by SPS. The CBMM Company supplied the niobium carbide powder (99% purity) with particle size lower than 27 µm. This powder was milled in a high-energy ball mill at 400 rpm using different times (90, 180, and 300 min respectively). AISI 52100 bearing steel balls were used during the milling in a cylindrical stainless steel with internal tungsten coating. Mechanical properties were carried out by hardness (HV 10 kgf) and fracture toughness measurements (Palmqvist method). The main results showed the efficiency of milling time on particle size reduction, up to 5 µm with 300 min of milling. Furthermore, particle reduction promoted densification during the sintering process and consequently improve mechanical properties. Best results of 300 minutes comminution presented hardness value of around 2400 HV and fracture toughness of 7.5 MPa.m^1/2.
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