Thermal stability of tungsten carbide in 7mol.% calcia–zirconia solid solution matrix heat treated in argon

Sintering, thermal stability and mechanical properties of ZrO2-WC composites obtained by pulsed electric current sintering

“…The present observation is consistent with the work of Chamberlain et al reporting the direct reaction of ZrO 2 and WC to be thermodynamically favorable only above 1960°C [12]. However, it is in contradiction with other literature reports, revealing the presence of ZrC, W 2 C and even W phases as reaction products in ZrO 2 -WC composites during pressureless sintering in vacuum for 1 h at ≥1750°C [13] and the formation of ZrC when PECS of WC composites with 10 vol.% ZrO 2 for 1.5-4 min at 1700°C and 1800°C [5]. These different observations can be directly related to the shorter interaction times during PECS densification compared to pressureless sintering and the relative phase contents.…”

Densification and microstructure development in spark plasma sintered WC–6 wt% ZrO2 nanocomposites

“…The presence of elemental W was detected in earlier studies on a similar system. 27,28 In the present work, the development of such finescaled microstructure in the WC-ZrO 2 nanocomposite can also be attributed to the high heating rate (600°C/min) and lower sintering temperature (1300°C). Because of the high heating rate, the final sintering temperature can be reached in less time.…”

“…This effect is similar to the results obtained for ZrO 2 -WC composite, where WC is present only in a small amount. 28 Observations of ZrO 2 in the grain interior and triple points of WC indicate considerable interaction during the sintering process between ZrO 2 and WC particles. The presence of W 2 C near the ZrO 2 -WC interface has been conclusively established through TEM analysis.…”

Effect of sintering environment on the structure of calcia-stabilised TiO2-added zirconia solid solutions

“…In this sequence, the increased amount of extra oxygen vacancies can be attributed to: (i) smaller oxygen partial pressure in the argon atmosphere (S/Ar samples) than in the air atmosphere (S/air samples), (ii) the presence of carbon from the graphite covers (HP/Ar and HP/Ar/WC samples) which can decrease the oxygen partial pressure in the surrounding atmosphere due to large chemical affinity of carbon to oxygen; the effects of carburisation of the zirconia solid solutions cannot be excluded, (iii) the presence of WC particulates (HP/Ar/WC samples) which increases the concentration of oxygen vacancies due to the beginning of the WC decomposition process induced by oxygen originating from the zirconia solid solution, as suggested by Moskała and Pyda studies. 3 The presented data indicate that factors inducing the lattice contraction predominated the subtle effects of the increased oxygen vacancy concentration. Residual surface stresses seem to be of great importance in this case.…”

“…1 However, the zirconia stoichiometry can be influenced not only by the sintering atmosphere of different oxygen partial pressure but also by any reaction which consumes or creates oxygen vacancies, e.g. intentional or unintentional carburisation combined with the carbon-alloying dopant reaction, 2 chemical reaction between reinforcement and zirconia particles, 3 etc. Such a reaction, which can accompany the sintering process of the zirconia based body, together with the sintering atmosphere, creates the sintering environment contributing to the resultant properties.…”