Load-carrying Capacity of the HB〓340 (Hardened and Tempered) Gears : 1st Report, Effect of Surface Roughness on the Rolling Contact Fatigue of the Rollers and Surface Durability of the Habbed Gears

Abstract

Surface durability of the H_B ≈ 340 (hardened and tempered) hobbed gears was investigated by using a 2-roller-type fatigue tester and a power circulating-type gear tester. It is found that the initial surface roughness has much more influence on the rolling contact fatigue of the H_B ≈ 340 steel than that of the H_B ≈ 150 (annealed) one, and therefore, that the pitting limit of the H_B ≈ 340 hobbed gears is P_max ≈ 0.2H_B kgf/mm² due to the rough initial surface. Thus, the tooth surface of the H_B ≈ 340 hobbed gears should be finished as smooth as possible in order to obtain higher surface durability by the effect of hardness.