14 June 2026 · 7 min read
Two materials come up again and again when discussing agricultural gearbox components: EN8 and 20MnCr5. They are not competitors so much as tools for different jobs. Choosing well means matching the material to how the part is loaded — and knowing when heat treatment changes the picture.
EN8 — a dependable medium-carbon steel
EN8 is an unalloyed medium-carbon steel valued for its balance of strength, machinability and cost. It is a sensible default for shafts, spacers, many general gears and components that see moderate loads. EN8 can be through-hardened and tempered to raise strength where a part needs it, and it machines cleanly, which keeps cost reasonable on bulk and replacement work.
Where EN8 reaches its limit is heavy, repeated tooth contact under shock loads. A through-hardened gear is hard all the way through, which can make the tooth more brittle than ideal for high-impact duty.
20MnCr5 — a case-hardening alloy for gears
20MnCr5 is a chromium-manganese alloy steel designed for carburizing (case hardening). After carburizing, the gear tooth has a hard, wear-resistant surface over a tougher, more ductile core. That combination — hard skin, tough heart — is exactly what a loaded gear tooth wants: resistance to surface wear and pitting on the outside, and the ability to absorb shock without cracking on the inside.
This is why higher-duty gears in assemblies such as the 5 Speed GDR gearbox and the 4 Speed GDR gearbox are commonly made from 20MnCr5 and carburized, while shafts in the same assembly are often EN8.
Why carburizing matters
Carburizing diffuses carbon into the surface of a low-carbon alloy before hardening, creating a hardened "case" of a controlled depth. The result is a part that resists the two things that kill gear teeth — abrasive wear and contact fatigue — without becoming brittle throughout. The case depth and hardness are chosen for the component and its duty.
How to specify the right material
- Moderate load, cost-sensitive, simple geometry: EN8, tempered if extra strength is needed.
- Loaded gear teeth, wear and shock: 20MnCr5, carburized.
- Shafts and supports within a gearbox: EN8 is common and economical.
- Unsure? Share the application, the failure mode of the old part (worn teeth vs cracked vs bent) and we will recommend a material as per requirement.
At DISHA GEARWORKS, gears are manufactured in 20MnCr5 and EN8 as per component requirement, with carburizing available where it adds value. Every assembly is inspected before dispatch and gearbox assemblies are tested.
Planning a gearbox or gear order? Explore our gearbox assemblies or request a quote with your sample, drawing or application details.
