Grain growth inhibition of hardmetals during initial heat-up. (April 2018)

• Record Type: Journal Article
• Authors: Pötschke, J.; Gestrich, T.; Richter, V.
• Is Part Of: International journal of refractory metals & hard materials. Volume 72(2018)
• Page Start: 117
• Page End: 125
• Publication Date: 2018-04
• Subjects: Hardmetals -- WC-Co -- Nanoscaled -- Grain growth inhibition -- Solid state sintering; 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.2017.12.016
• Languages: English
• ISSNs: 0263-4368

Abstract

Abstract: Ultrafine and nanoscaled hardmetals show a significant grain growth already before reaching liquid phase sintering temperature. To limit grain growth during this stage of sintering the known grain growth inhibitors, mostly metal carbides like Cr3 C2 or VC can be used. To investigate grain growth inhibition and dissolution of these carbides both the solid state sintering without Co (binderless tungsten carbide) and with 10 wt-% Co were investigated in the temperature range between 600 °C and 2000 °C and 1500 °C, respectively. It could be shown that e.g. the Cr3 C2 starts to decompose already below 800 °C into a Cr-rich and C-rich phase. In both types of material with and without Co this leads to earlier reduction of W-oxides and the formation of Cr-based oxides which alter the chemical processes during sintering and change the grain growth behaviour. By using thermoanalytical methods as well as interrupted sintering experiments and their characterisation by FE-SEM and XRD, the direct influence of Co and grain growth inhibitors regarding the change in the chemical processes happening during sintering was studied. Highlights: Grain growth inhibition in ultrafine/nanoscaled hardmetals was studied. Interrupted sintering experiments were carried out between 600 °C to 2000 °C. Effect of carbide addition (VC, Cr3 C2 ) was investigated by FESEM, XRD, thermoanalytical methods. Grain growth inhibition hardmetals happens already below liquid phase formation.