Effect of Al2O3-NbC nanopowder incorporation on the mechanical properties of 3Y-TZP/Al2O3-NbC nanocomposites obtained by conventional and spark plasma sintering

Abstract

The effect of incorporation Al2O3-NbC nanopowders to reinforce 3Y-TZP matrix and the influence on mechanical properties of 3YTZP-Al2O3-NbC nanocomposites obtained by conventional and spark plasma sintering (SPS) was investigated. The nanometric powders of Al2O3-NbC were prepared by reactive high-energy milling, deagglomerated, leached with acid, and added to the 3Y-TZP matrix in the proportion of 5 vol%. The final powders were dried under airflow, compacted and sintered at the temperature range of 1300-1500 °C. The effect of sintering technique and final temperature on the microstructure and mechanical properties, such as hardness, toughness and Young's modulus were analyzed. An important mechanical value obtained in all materials reinforced with Al2O3-NbC nanopowders is the fracture toughness, which differ significantly of the 3Y-TZP monolithic material (5.2 MPa•m 1/2). The nanocomposites sintered conventionally at 1450°C show the higher fracture toughness (8.7 MPa•m 1/2). Microstructure observations indicate that NbC nanoparticles are dispersed homogeneously within 3Y-TZP matrix and limited their grain growth. However, the partial oxidation of the NbC in the surface of the nanocomposites found a limit in the conventional sintering temperature, since the samples sintered at 1500°C showed a reduction in fracture toughness.

Dry‐sliding wear behavior of 3Y‐TZP/Al2O3‐NbC nanocomposites produced by conventional sintering and spark plasma sintering

“…However, comparing both counter‐materials, the friction coefficients were generally higher in the tests with the WC‐6%Co ball, while the wear rate was lower in the tests performed with the Al 2 O 3 ball. In the case of the nanocomposites sintered by SPS at 1350°C, the toughness measured was significantly lower (6.3 ± 1.0 MPa.m 1/2 ) than the other tested temperatures. Thus, despite higher hardness and density, this led to the formation of more debris, especially during the test with the Al 2 O 3 counter‐material, which can be the reason for such higher friction coefficients.…”

“…Thus, despite higher hardness and density, this led to the formation of more debris, especially during the test with the Al 2 O 3 counter‐material, which can be the reason for such higher friction coefficients. This was not observed in the samples sintered at 1400 and 1450°C and tested with Al 2 O 3 counter‐materials, which presented toughness above 8.0 MPa.m 1/2 . Also, the formation of protective layers and the predominance of less aggressive wear mechanisms could have prevented higher friction coefficients for these samples, while this was not observed during the tests with WC‐6%Co counter‐materials.…”

“…In this study, nanocrystalline Al 2 O 3 ‐NbC powders were synthesized by reactive high‐energy milling as described in previous reports . To produce the 3Y‐TZP/Al 2 O 3 ‐NbC nanocomposites, 5 vol% Al 2 O 3 ‐NbC powder was added to commercial 3Y‐TZP powder (TZ‐3Y‐E; Tosoh, Tokyo, Japan), with mean particle size of 40 nm, using ball milling, according to our previously published paper . The composite mixtures were obtained in a conventional ball mill in an alcoholic suspension of 0.2 wt% para‐aminobenzoic acid (PABA) and 0.5 wt% oleic acid.…”

“…The microstructural characterization of the fracture surfaces of sintered nanocomposites was performed using a field emission gun scanning electron microscope (FE‐SEM Ultra55; Zeiss, Jena, Germany). Measurements of physical and mechanical properties of the sintered materials, such as density, Young's modulus, microhardness, and toughness were also performed and published in our previous work …”

“…These materials have high hardness, elastic modulus, and melting point and thus play an important role in the wear performance of 3Y‐TZP‐based composites in applications such as bearings, cutting tools, and punching and stamping dies. In particular, 3Y‐TZP reinforced with Al 2 O 3 and NbC nanoparticles have been recently investigated, with promising results . The mechanical properties of a composite are strongly dependent on its microstructure, which are a result of the raw materials used and the processing technique .…”