MECHANICAL PROPERTIES OF GROUP VI CARBIDES

The mechanical properties of Group VI carbides are summarized in Table 6.5. The values are average values reported in the recent litera-turel lPlI W7] (see Sec. 4.1 of Ch. 4). 

Compound Vickers Hardness (GPa) Young s Modulus of Elasticity (GPa) Shear Modulus (GPa) Transverse Rupture Strength (MPa) 

The fracture mechanism and the ductile-brittle transition are similar to those of the carbides of Groups IV and V (see Sec. 4, Ch. 4). The high strength of WC should be noted. 

Hardness. Table 6.5 shows that carbides of Group VI are not as hard as the carbides of Groups IV and V (see Ch. 4, Table 4.6 and Ch. 5, Table 5.6). This may reflect the lower strength oftheirM-C bonds. The hardness decreases with temperature as shown in Fig. 4.6 (Ch. 4). Alone among the refractory carbides, WC retains its hardness up to approximately 800°C and, above 400°C, it is the hardest carbide. 

---