Grinding cracks on gear flank. Photo courtesy GEARTECH © 2014.
Definition: Grinding cracks occur during the grinding process.
Identification: Grinding cracks occur on ground surfaces, usually perpendicular to the grind direction. They are relatively shallow and parallel or in a crazed pattern.
Discussion: The grinding process generates a large amount of heat. If the process is not correctly controlled, or if coolant flow is not adequate, grinding cracks can result. High levels of retained austentite can also load up the grinding wheel, making grinding cracks more likely to occur.
Prevention: Use proper wheel, feed, speed, and coolant.Keep gear retained austenite level at or below 20%. Keep case free of carbide networks. Keep gear surface hardness below 60 HRC.