Air carrier Captain reported receiving indications of hot brakes during taxi. With brake temperature reaching over 305 degrees C; the crew stopped the aircraft an consulted maintenance who indicated a main wheel bearing had failed.

Narrative

Push back normal. On initial taxi; I needed breakaway thrust of 7%. 5 minutes into taxi; brake temp on wheel 2 was rising higher than other brakes. Approximately 150 Degrees C. After 8 minutes of taxi; we arrived at Runway XXL. Taxi speed was between 10-20 kts. Temperature on wheel 2 was now 305 Degrees C along with 'Brakes Hot' ECAM.We noticed we were close to our Maintenance hangar; so we decided to taxi onto the ramp for maintenance inspection. They confirmed we had Hot Brakes and not an indication issue. After waiting approximately 1 hour for brake to cool below 150; we were towed back to the gate. Brake temperature continued to rise on #2 wheel during tow; but did not reach 300 Degrees C.Upon maintenance inspection; the #2 wheel bearing broke into pieces. These pieces were ground between wheel; axle sleeve; and bearings which caused friction and rise in temperature. The wheel; brake assembly; and axle sleeve will need to be replaced.Maintenance said if we tried to takeoff; wheel assembly would've come apart; along with a brake fire.