Silicon Carbide Seals

			Silicon Carbide
Material properties	Norm	Symbol/Unit	F	F plus	T
Density	DIN EN 623-2	ρ [g/cm3]	>3.10	>3.16	>3.21
Porosity	DIN EN 623-2	P [%]	<3.0	<1.0	<1.0
Mean grain size		[μm]	<5	<5	<2
Grain size distribution		[μm]
Phase composition			α-SiC	α-SiC	α-SiC, YAG
Vickers hardness	DIN EN 843-4	HV 1 [GPa]	25.5	25.5	22.5
Knoop hardness	DIN EN 843-4	HK 0.1 [GPa]	24.5	24.5	21.0
Young's modulus	DIN EN 843-2	E [GPa]	410	420	420
Weibull modulus	DIN EN 843-5	m	10	15	15
Flexural strength, 4-pt bending	DIN EN 843-1	σB [MPa]	400	510	550
Compressive strength		σD [MPa]	2200	2200	2500
Poisson ratio		ν	0.17	0.17	0.16
Fracture toughness (SENB)		Klc [MPa·m0,5]	4	4	6
Coefficient of thermal expansion	DIN EN 821-1
20°C - 500°C		α [10-6/K]	4.1	4.1	3.5
500°C - 1000°C		α [10-6/K]	5.2	5.2	5.2
Specific heat at 20°C	DIN EN 821-3	cp [J/g K]	0.6	0.6	0.6
Thermal conductivity at 20°C	DIN EN 821-2	λ [W/mK]	125	125	75
Thermal stress parameters	calculated
R1 = σB·(1-ν) / (α·E)		R1 [K]	198	246	314
R2 = R1·λ		R2 [W/mm]	25	31	24
Specific electrical resistance at 20°C	DIN EN 50359	ρ [Ω cm]	106-108	106-108	102-103

			Silicon Carbide
Material properties	Norm	Symbol/Unit	C	P	G
Density	DIN EN 623-2	ρ [g/cm3]	>3.10	>2.76- 2.89	>3.02
Porosity	DIN EN 623-2	P [%]	<3.0	10-14	<3.0
Mean grain size		[μm]	bimodal	<5	bimodal
Grain size distribution		[μm]	10-1500		10-1000
Phase composition			α-SiC	α-SiC	α-SiC, graphite
Vickers hardness	DIN EN 843-4	HV 1 [GPa]	25.5	23.5	24.5
Knoop hardness	DIN EN 843-4	HK 0.1 [GPa]	24.5	21.6	23.0
Young's modulus	DIN EN 843-2	E [GPa]	410	340	390
Weibull modulus	DIN EN 843-5	m	10	15	14
Flexural strength, 4-pt bending	DIN EN 843-1	σB [MPa]	400	225	230
Compressive strength		σD [MPa]	2500	2000	2500
Poisson ratio		ν	0.17	0.17	0.16
Fracture toughness (SENB)		Klc [MPa·m0,5]	3.5	3	3
Coefficient of thermal expansion	DIN EN 821-1
20°C - 500°C		α [10-6/K]	4.1	3.5	4.0
500°C - 1000°C		α [10-6/K]	5.2	5.6	5.0
Specific heat at 20°C	DIN EN 821-3	cp [J/g K]	0.6	0.6	0.6
Thermal conductivity at 20°C	DIN EN 821-2	λ [W/mK]	125	90	110
Thermal stress parameters	calculated
R1 = σB·(1-ν) / (α·E)		R1 [K]	198	157	124
R2 = R1·λ		R2 [W/mm]	25	14	14
Specific electrical resistance at 20°C	DIN EN 50359	ρ [Ω cm]	103-104	106-108	103-104