Does silicon carbide float?

No. At 3,210 kg/m³ it is denser than water.

Silicon carbide

Density of silicon carbide

3,210 kg/m³

3.21 g/cm³ · 200.4 lb/ft³

It does not melt: at atmospheric pressure it sublimes and decomposes above about 2700 °C, which is why no melting figure is given here. Harder than alumina at Mohs 9.5 and with four times the thermal conductivity, so it survives thermal shock that would shatter a comparable alumina part, and it is the standard kiln shelf material for that reason. Its wide bandgap has made it the material of choice for electric vehicle traction inverters, where SiC transistors switch faster and run hotter than silicon.

Properties

Density: 3,210 kg/m³ — 3.21 g/cm³
Tensile strength: 250–400 MPa
Young's modulus: 410 GPa
Thermal conductivity: 120 W/(m·K)
Hardness: 9.5 Mohs
Thermal expansion: 4 µm/(m·K)
Floats in water: No
Magnetic: No

What it is used for

Abrasive paper, wheels and lapping compound
Kiln shelves and furnace elements
Mechanical seal faces and pump parts
High-voltage power semiconductors

How it compares

Water is 1,000 kg/m³. Anything with a shorter bar than water floats in it.

air 1.2 kg/m³

expanded polystyrene foam 20 kg/m³

rigid polyurethane foam 40 kg/m³

Water — the float line 1,000 kg/m³

silicon carbide 3,210 kg/m³

tungsten 19,250 kg/m³

gold 19,300 kg/m³

platinum 21,450 kg/m³

Water is 1,000 kg/m³. Anything below that floats.
Material	Density	Relative to water
rigid polyurethane foam	40 kg/m³	0.04×
expanded polystyrene foam	20 kg/m³	0.02×
air	1.2 kg/m³	0.00×
silicon carbide ←	3,210 kg/m³	3.21×
platinum	21,450 kg/m³	21.45×
gold	19,300 kg/m³	19.30×
tungsten	19,250 kg/m³	19.25×

Does it rust?

Silicon carbide contains no iron, so it cannot rust. Whether it degrades depends on the material, not on oxidation.

Is it magnetic?

Silicon carbide is not a metal and has no ferromagnetic response.

Common questions

What is the density of silicon carbide?: 3,210 kg/m³, or 3.21 g/cm³.
Does silicon carbide float?: No. At 3,210 kg/m³ it is denser than water.
Is silicon carbide magnetic?: Silicon carbide is not a metal and has no ferromagnetic response.

Does silicon carbide float? No
Concrete 2,400 kg/m³
Brick 1,900 kg/m³
Gypsum board (drywall) 700 kg/m³
Tungsten carbide 14,900 kg/m³
Reinforced concrete 2,500 kg/m³
Graphite 2,200 kg/m³
Porcelain 2,400 kg/m³
Plaster 1,100 kg/m³

Sources

Typical range compiled from manufacturer specifications — At One Place

How these figures are compiled and checked