Nitriding is a surface treatment process that can be applied to a variety of machine components. The process provides a very hard surface while maintaining a “tough” core and tight tolerances can still be achieved. This process is applied at low temperatures so that part distortion is not an issue. Nitriding is often the final step in the manufacturing process of the part.
An alternative process is through hardening. However, this process requires higher cost material and the part must be ground to achieve final dimensions
Examples:
- Gear industry: Can be classified as a case hardening process
- Typical hardness – Rockwell C 55 or greater
- 0. 0.020 inches or deeper
- Gears, shafts, spindles, machine tools
- Rails and Machine Ways (where a wheel or roller rides on the parts)
- Applied to the area of wear
- Coupling industry: used to connect parts for steel mills
- Sliding gear teeth are hardened to minimize wear
- Plastic injection screws, barrels and molds: Nitriding parts up to 22 feet in length
- Wind energy market – Gears and bearings vs. conventional carburizing or through hardening
- Trying to avoid distortion
Some interesting customer examples would include nitriding submarine gears. The US military needed to harden a gear that was so large the submarine had to be built around the part. Metlab used the nitriding process on the gear which weighed 12,000 lbs.
Large submarine gear is being prepared for Nitriding.
Three bevel gears which have been Nitrided
Another example is the large gear that turns the turret of the Merkava tank, manufactured by an Israeli defense company. Each gear is 96 inches in diameter. Earlier gears were flame hardened, which resulted in some premature failures of the turret gear teeth. With nitriding, there has never been a single failure of the part.
Metlab provides metallurgical consulting to guide customers to the correct process to meet the required specifications. The Metlab facility has nitriding capabilities for parts that are up to 12 feet tall by 14 feet diameter or four feet in diameter by 22 feet long. It also has a small nitriding furnace, three feet in diameter by three feet long, for rush, non-scheduled production. The company services customers primarily in North America and runs the nitride furnaces twice a week, or as needed based on customer demand.
Mark Podob
Vice President – Metlab
Heat Treating – Surface Treatment – Metallurgical Consulting
mpodob@metlabheattreat.com
