Patent ID: 7384488

Claim:
A method comprising following steps in sequence for producing both superior bending fatigue strength and pitting fatigue life of gear(s) and/or shaft components made of steel: (a) applying a carbonitriding treatment, comprising the following steps in sequence: carburizing at 900 to 1050 degree Centigrade, cooling down to 840 to 870 degree Centigrade for carbonitriding with 15 to 20% ammonia, quenching in a medium at 120 to 150 degree Centigrade, tempering at 160 to 180 degree Centigrade; and (b) applying a hard shot peening process having the following process parameters: shot size ranging from 0.5 to 0.8 mm, shot hardness ranging from 610 to 800 Hv, and shot velocity ranging from 60 to 150 m/sec.