Effect of Milling on the Carbothermal Reduction of Oxide Mixture for (Ti,W)C-Ni

Abstract

The effect of high-energy milling on the phase transformation and carbothermal reduction was examined using an oxide mixture, TiO 2 -WO 3 -NiO-C, with a process to synthesize (Ti,W)C cermets. Due to the high energy involved in the mill raw, anatase TiO 2 transformed first to TiO 2 -II and then to rutile, while WO 3 transformed to a high-pressure WO 3 -HP and hexagonal WO 3 phase. The co-existence of WO 3 and TiO 2 enhanced the formation of a nano-crystalline or amorphous phase. The (Ti,W)C phase was formed mainly at 1150 C from TiC and WC formed in the early stages. These results were further examined using XRD, the Rietveld method and mass spectroscopy.

WC-reinforced (Ti,W)(CN)

“…[3][4][5][6][7][8] The synthesis of (Ti,W)(CN) powders, through high-energy ball milling and carbothermal reduction of oxide mixtures, is well described elsewhere. [9][10][11][12] The presence of the metallic phase, which was introduced from the milling media, enabled the densification of (Ti,W)(CN) at low temperatures without external pressure.…”

Thermodynamic stability of in situ W–ZrC and W–Zr(CN) composites

“…1a shows that the oxide phases remained, and were not converted completely to carbide after reduction heat-treatment at 1300 C. When ZrO 2 is carbothermally reduced, intermediate phases, such as ZrO and Zr 2 O, are evident during the reduction process. ZrO 2 is expected to be converted to ZrO, then to Zr(CO), and finally to ZrC in a similar way to that previously observed for TiO 2 [29,30]. Complete carburization of ZrO 2 requires high temperatures (as shown in Fig.…”

Microstructure of (W,Ti)C–Co system containing platelet WC

“…As mentioned in the previous section, the (1 0 1) prism plane develops preferentially in (W 0.9 Ti 0.1 )C powder, which serves as a base for the thin platelet morphology. Our previous studies [18,19] reported that WC forms between 600 and 800 • C from milled mixtures of WO 3 and C, while TiC forms around between 1000 and 1200 • C from milled mixtures of TiO 2 and C. Therefore, it is more likely that (W,Ti)C is expected to form first at a low temperature and followed by the (Ti,W)C formation (between 1000 and 1200 • C). This view is supported by the XRD results in Fig.…”