Failure of the pinion from the drive of a cement mill

The pinion from the drive of the cement mill was failed; the teeth cracked and spall occurred on the sides of several teeth. The failure was only located on one side of the pinion. This type of failure is common with surface-hardened gears. e found that the failure of the pinion is a direct consequence of the incorrect geometry of the surface hardened layer. The lifespan of the pinion could have been extended if the whole surface of the faces and roots of the teeth had been hardened and if the hardening had been deeper.