Components resistant to marine corrosion through CRA coatings
Corrosion Resistant Alloys, also CRA, are known for their properties against this phenomenon and are widely used in components that are exposed to particularly corrosive environments. However, in most cases, their price and other requests or requirements of the parts make itunfeasible these part to be manufacture in these materials.
The development and manufacture of multi-material components is possible thanks to the evolution of manufacturing technologies, which allow the incorporation of corrosion properties in the functional surface of the parts. In this way, it is possible to separate the structural function and the function of resistance against corrosion through the development of protective surfaces based on CRA adapted to each medium. That way, a higher performance in service is achieved at a lower cost.
This case study presents the development of advanced anti-corrosion coatings through the application of CRA powder developed ad-hoc on the surface of the components.
Approach
Aim:
Substitution of solid CRA components by a mixed solution, with a high-strength steel core and surface recharged with CRA.
Base material::
1.7227 steel in high strength quenched and tempered condition:
- Yield strength: 980 MPa.
- Mechanical resistance: 1,200 MPa.
Refill materials:
Ad-hoc CRA alloys with PREN between 24 (low alloy levels and lower cost) and 44 (high alloy level and cost).
Protection typology:
0.7 mm thick monolayer.
Fields of action:
- Ad-hoc CRA development
- Development of application parameters
- Characterization and study of performance
Main results
- Homogeneous microstructure in the overlay and homogeneous thicknesses.
- Similar open circuit potential values.
- With PREN 32, values similar to the CRA biting potential of PREN 44 and higher than that of PREN 24 are obtained.
Conclusions
- Obtention of homogeneous surfaces by recharging. Feasibility of creating “ad hoc” surfaces.
- Using laser cladding technology, it is possible to optimize the PREN level to respond to hostile environments, without the need to oversize the investment in alloy elements.
- There is a trade-off between corrosion properties and mechanical properties when using the PREN CRA intermediate.