Gas nitrocarburization: The best protection for bearing bolts?
By Lars Butenschon (Edited by Shizu Yamaguchi)
Corrosion protection for shafts and bearing bolts is critically important, especially in applications where the bearing point cannot be lubricated (for example in machines in the construction industry). Although galvanized shafts are often used to solve this lubrication challenge, they often prove insufficiently corrosion resistant when paired with plain bearings.
To identify more suitable shafts, we carried out extensive tests on various coatings and compared their performance. Qualities we also tested for included wear resistance, corrosion resistance, and low-cost options.
On the test bench: different shaft coatings in the salt spray test
The gold standard for corrosion testing is the salt spray test. In this test, the corrosion process is significantly accelerated by spraying salt water on shafts in a chamber, enabling the corrosion resistance of surfaces to be assessed in a comparatively short time.
We tested bearing pins made from quenched and tempered 42CrMo4 steel in 3 conditions:
- Untreated
- Gas nitrocarburized
- Gas nitrocarburized with additional post-oxidation
All bearing bolts had already been operated prior to the salt spray test so that any running-in marks from the bearings could also be considered.
To evaluate the influence of wear and running-in marks from different bearing materials, 2 variants were tested in each case: shafts previously run with iglide® G plain bearings and shafts previously run with iglide® TX1 bearings. The shafts were exposed in the salt spray chamber for 120 hours and then examined.
A clear result
The results of the salt spray test clearly show that shafts with nitrocarburization and additional post-oxidation provide by far the best corrosion protection. Shafts treated only by gas nitrocarburization offered limited corrosion resistance, while untreated bolts corroded most severely. For this reason, gas-nitrocarburized and post-oxidized steels are strongly recommended for unlubricated bearing pins operating in humid environments.
Next steps
Whether you need help selecting the right corrosion protection for shafts and bearing bolts or designing the entire bearing point, we can support you free of charge and without obligation. Reach out to us!
