Microstructure Evolution in the Cemented Carbides WC-Co II. Cumulated Effects of Cr Additions and of the C/W Ratio on the Crystal Features of the WC Grains

Cr-rich layer at the WC/Co interface in Cr-doped WC–Co cermets: segregation or metastable carbide?

“…In the W-rich one, steps consist of a flat habit plane (prismatic or basal) and a rounded part. These observations confirm those previously reported [6]. The WC grain size in the first alloy was not measured but is much finer than in the second type.…”

“…The alloys, prepared from WC powder with 0.91 mm in size, were liquid-phase sintered at 1450 C, 120 min using the processing conditions described in detail in Ref. [6]. In the temperature interval 600-1450 C, the heating time, 230 min, is longer and the cooling time, about 10 min, is shorter than for the first type of alloy.…”

“…In the temperature interval 600-1450 C, the heating time, 230 min, is longer and the cooling time, about 10 min, is shorter than for the first type of alloy. HREM was effected on slices extracted from the materials previously studied [6].…”

“…Cr, added as Cr 3 C 2, is one of the elements that limit grain growth during the sintering process but also slower densification [5]. The Cr effect is related to the C potential in the alloy: in C-rich alloys, Cr is less efficient than in W-rich alloys and abnormal growth occurs [6,7]. To understand the role of Cr in the growth inhibition, its distribution in the alloy was investigated by different techniques.…”

“…The previous transmission electron microscopy (TEM) study by the present authors showed that Cr modifies the WC grain morphology, giving rise to rounded interfaces and interface steps depending on the C content [6]. The aim of the present work is to determine if the Cr enrichment detected at the WC/Co interfaces [10,16] results of a Cr segregation in the binder or of a Cr-rich phase.…”