Investigation of Scaling and Materials’ Performance of EHLA Fabricated Cladding in Simulated Geothermal Brine

This study investigates the corrosion and scaling behaviour of Extreme High-speed Laser Application (EHLA)-fabricated corrosion-resistant alloy (CRA) claddings under simulated geothermal brine conditions. EHLA 316L stainless steel and alloy 625 coat-ings were produced and tested in simulated brine (Chloride–carbonate–silica geo-thermal brine) at 70°C for 720h to evaluate the influence of additive manufacturing microstructures on corrosion performance. The EHLA coatings exhibited dense, met-allurgically bonded microstructures with minimal porosity. Microstructural analysis revealed Nb- and Mo- rich segregation in EHLA 625 and fine columnar dendritic morphology in all coatings. EHLA 625 also displayed stable passive film formation but had a thin deposit of Mg-O-containing compounds from the brine. EHLA 316L on the other hand exhibited localised pitting and heavy Si- and Mg-containing scale accumu-lation, especially in as-built conditions. Surface finishing reduced corrosion activity by minimizing roughness and defect-driven localised attack. Critical pitting temperature tests confirmed the superior localised corrosion resistance of EHLA 625 compared to EHLA 316L. However, further process improvements and perhaps post-deposition thermal treatments might be required to bring the performance of the coatings in line with the wrought alloys. The results demonstrate that EHLA-fabricated coatings offer corrosion and scaling resistance. This coating technique has the potential to provide cost-effective solutions to produce corrosion resistant coatings on geothermal components.