Contact and bending endurance limits

Heat treatment	Tooth hardness	Gear material
case	core and root
Normalizing, martempering	Brinell 180 to 350	Carbon and alloy steels, such as 45 (0.45C), 40X (0.40C-Cr), 40XH (0.40C-Cr-Ni), 50XH (0.50C-Cr-Ni), and 35XM (0.35C-Cr-Mo)
Full hardening	Rockwell C, 40 to 55	Carbon and alloy steels, such as 45 (0.45C), 40X (0.40C-Cr), 40XH (0.40C-Cr-Ni), and 35XM (0.35C-Cr-Mo)
Surface hardening	Rockwell C, 40 to 58	Rockwell C, 25 to 35	Alloy steels, such as 40X (0.40C-Cr), 40XH (0.40C-Cr-Ni), 50XH (0.50C-Cr-Ni), and 35XM (0.35C-Cr-Mo)
Case hardening	Rockwell C, 54 to 64	Rockwell C, 30 to 45	Alloy steels, such as 20XH2M (0.20C-Cr-2Ni-Mo)
Nitriding	Rockwell C, 50 to 60	Rockwell C, 24 to 40	Alloy steels, such as 40XH2MA (0.40C-Cr-2Ni-Mo, quality)		(of tooth core)

Determine the base number of stress cycles for the pinion and gear . For this purpose we use table 2.2.

Table 2.2