Hypoid Drive Pinion – TSH Process vs Gas Carburized


The conventional heat treat process for hypoid drive pinion is gas carburizing.  Conventional induction contour hardening is not practical due to the complex part geometry.  The TSH technology makes induction contour hardening of this part possible.

TSH Processed Gas Carburized
Steel 60LH 8625H
Total Cycle Time 3 minutes 12 hours
Surface Hardness 58-63 HRC 58-62 HRC
Case Depth 1.0-1.5 mm 1.0-1.5 mm
Core Hardness 30-45 HRC 25-45HRC
Case Microstructure


Grain Size

Grain Boundary Oxidation

Nonmartensitic Surface Layer

Fine grain lath martensite

GS# 9-14



High carbon plate martensite

GS# 5-8

10-25 microns

10-25 microns

Core Microstructure Bainite and fine pearlite Low carbon lath martensite and bainite
Residual Stress High Compressive (600-1000Mpa) Low Compressive (140-300 Mpa)
Fatigue Life 2-3X 1
Shot Peening Eliminated Needed

TSH through heating

TSH Heating