Cold-formed coatings: durability in aggressive environments
Presentation of the results of research conducted on the application of L-DED (laser deposition) technology to create hybrid threaded fasteners composed of a high-toughness carbon steel core (10.9 32CrB4 grade) and two types of 1.5mm coatings of maraging steels (C300, 15–5 PH, and 17–4 PH grades), which are more resistant to marine corrosion.
The results show that, in addition to improving corrosion protection, the coatings improved high-cycle fatigue performance compared to the fastener manufactured entirely from 32CrB4 steel used as a reference..
- 50% of the coated fasteners tested in this study showed fatigue wear after 5 × 106 cycles
- The average fatigue life of the coated samples was approximately 3.5 × 106 cycles (three times longer than the reference sample, with an average fatigue life slightly higher than 1 × 106 cycles ).
It has been observed that L-DED coating application does not restrict subsequent turning and thread rolling operations, nor does it require additional finishing steps.
The session also shared some guidelines related to the manufacturing process:
- Minimizing dilution and the number of layers is essential to achieving favorable results in bolts with stainless steel skins and hardened and tempered steel cores.
- Cold rolling after precipitation treatment is key to improving the fatigue life of hardened fasteners.
- The advantages offered by this solution increase with the higher metric dimensions of the fastener.
- This solution potentially extends the service life of fasteners or the workloads they can withstand.
The content of this presentation is based on the research work: “Improvement opportunities on fatigue and corrosion behaviors in offshore fastener threads combining a maraging steel skin with a class 10.9 32CRB4 core” (DOI: 10.1007/s00170-025-15439-5)
Author:
Garikoitz Artola (AZTERLAN)
Keywords:
L-DED, corrosion behavior, fatigue resistance, fracture mechanisms, high-strength fastening, wind energy, coatings, forging.