What is gear hardness?
The hardness of gearing depends on the hardness of various materials and heat treatment methods, and is generally expressed in units such as HRC, HB, and HV.
Heat treatment is a process of heating and cooling a metallic material at an appropriate temperature for sufficient time to give it the required microstructure and mechanical properties such as hardness and toughness.
The expected hardness of gears made of several materials after various heat treatments is as follows.
No heat treatment :
- S45C (carbon steel for machine structural use) 194HB or less
Tempering :
- S45C (carbon steel for machine structural use) 200 - 270 HB
- SCM440 (chrome molybdenum alloy steel) 225 - 352 HB
Carburized and quenched :
- SCM415 (Chrome molybdenum alloy steel) 55 - 63 HRC
Induction hardening :
- S45C (carbon steel for machine structural use) 50 - 60 HRC
- SCM440 (chrome molybdenum alloy steel) 50 - 60 HRC
The hardness of gears after heat treatment described above is for reference only.
Hardness Tester