Sintering Behavior, Microstructure, and Mechanical Properties: A Comparison among Pressureless Sintered Ultra-Refractory Carbides

Table 2

Densification data for the samples pressureless sintered at 1950°C/60 min in flowing Ar; Mean grain size of the matrix and mechanical properties of the composites: hardness (HV1.0), Young’s modulus (E), fracture toughness (K_Ic) by CNB method, and 4-pt flexural strength (σ) at room and high temperature.

Label	Composition Vol%	Green Density %	Exp. Density g/cm^3	Th. Density g/cm^3	Relative density %	M.g.s. μm	HV1.0 GPa	E; GPa	KIc MPa·m^1/2	σ RT MPa	σ 1200^∘C MPa	σ 1500^∘C MPa
ZC0	100ZrC	63.9	4.81	6.63	~73	3	—	—	—	—	—	—
ZC5	95ZrC+5MoSi2	66.4	5.52	6.62	83.4	—	—	—	—	—	—	—
ZC10	90ZrC+10MoSi2	63.4	6.11	6.60	92.7	—	—	—	—	—	—	—
ZC20	80ZrC+20MoSi2	65.2	6.36	6.57	96.8	6	12.7±1.0	346±4	3.5±0.2	272±12	156±6	—
HC	100HfC	57.1	8.78	12.69	~70	1.5	—	—	—	—	—	—
HC5	95HfC+5MoSi2	55.8	12.13	12.37	98.1	4	15.6±0.6	434±4	3.62±0.13	465±45	408±31	241±112
HC10	90HfC+10MoSi2	55.6	11.79	12.05	97.8	3	16.1±0.4	415±4	3.53±0.29	452±90	357±21	306±18
HC10*	90HfC+10MoSi2	56.5	11.94	12.05	99.1	2	16.5±0.5	—	—	538±22	—	—
HC20	80HfC+20MoSi2	55.2	11.01	11.41	96.5	3	15.5±0.9	385±4	3.43±0.34	383±74	350±78	299±71
TC0	100TaCC	57.1	13.25	14.50	~91	6
TC5	95TaC+5MoSi2	58.5	13.09	14.09	92.9	6
TC10	90TaC+10MoSi2	58.2	13.45	13.67	98.4	5	12.5±0.8
TC20	80TaC+20MoSi2	56.6	12.32	12.86	95.8	7	12.1±0.7	476±4	3.83±0.14	591±61	—	—

∗After powders ultrasonication.