Microstructure and mechanical properties of NbC-matrix hardmetals with secondary carbide addition and different metal binders. (January 2015)

• Record Type: Journal Article
• Authors: Huang, S.G.; Vanmeensel, K.; Mohrbacher, H.; Woydt, M.; Vleugels, J.
• Is Part Of: International journal of refractory metals & hard materials. Volume 48(2015:Jan.)
• Page Start: 418
• Page End: 426
• Publication Date: 2015-01
• Subjects: Niobium carbide -- Sintering -- Grain growth -- Microstructure -- Mechanical properties; Heat resistant alloys -- Periodicals; Refractory materials -- Periodicals; Metallography -- Periodicals; Alliages réfractaires -- Périodiques; Matériaux réfractaires -- Périodiques; Métallographie -- Périodiques; Heat resistant alloys; Metallography; Refractory materials; Periodicals; Electronic journals; 669.73
• DOI: 10.1016/j.ijrmhm.2014.10.014
• Languages: English
• ISSNs: 0263-4368

Abstract

Abstract: NbC has a relatively high hardness (19.6 GPa) and melting temperature (3600 °C) and is usually applied as a grain growth inhibitor in WC–Co hardmetals. The current study reports on the influence of the sintering technology and overall chemical composition on the microstructure and mechanical properties of NbC-based hardmetals, using Co as a binder. The partial replacement of NbC by 5 wt.% WC, Mo2 C, VC or TiC allows one to significantly improve the hardness and toughness of the NbC–Co materials. The influence of different binders, i.e., Co, 316L stainless steel and Fe3 Al on the microstructure and mechanical properties of NbC-based hardmetals was also investigated. The powder mixtures were sintered in the solid state by PECS and liquid state by conventional vacuum sintering. Detailed microstructural analysis was conducted by EPMA elemental mapping and WDS point analysis. Mechanical properties, including Vickers hardness and indentation toughness were assessed. Highlights: NbC based hardmetals with different metal binders, i.e. Co, stainless steel and Fe-Al were prepared and fully densified by pressureless liquid phase sintering. Replacing Co binder by 316 L steel increases significantly the hardness of the liquid phase sintered hardmetal at comparable toughness. The influence of secondary carbides, WC, Mo2 C and VC on the microstructure and mechanical properties of NbC-12 wt% Co hardmetals was investigated. It was found the carbides exhibited a significant different solubility in the binder and NbC phases. It is able to adjust the microstructure and commitment properties of NbC based hardmetals by secondary carbide addition and alternative binder.