NobelClad and VDM Metals have been partners for a long time with regards to our high-performance nickel alloys. In a recently published paper, NobelClad presented its analysis of VDM® Alloy 825 from various points of view. 

The material: VDM® Alloy 825 

VDM® Alloy 825 is a titanium-stabilized, fully austenitic nickel-iron-chromium alloy with added copper and molybdenum. The alloy is highly resistant to chloride-induced stress corrosion and moderately resistant to chloride-induced pitting and crevice corrosion and oxidizing and non-oxidizing hot acids. In continuous operation at temperatures up to 550°C, VDM® Alloy 825 maintains toughness, which is why the alloy is VdTÜV and ASME approved for pressure vessels.

Beyond pressure vessel equipment, many industries rely on VDM® Alloy 825’s versality to construct reliable, safe applications. The alloy is used to build pipes, tubes, fittings, heat exchangers, evaporators and scrubbers in oil and gas production. In chemical processing, you can find VDM® Alloy 825 in sulfuric acid pickling and phosphoric acid manufacturing operations. 

Together, NobelClad and VDM Metals conducted a series of tests and building a case for N 825 cladded plates as a high-quality, reliable clad for highly corrosive pressure vessel environments. The companies set out to prove CRA properties can withstand cladding, head forming, and vessel manufacturing.

VDM® Alloy 825 cladded plate from NobelClad and VDM Metals: predictive corrosion properties

After setting the right parameters for steel, it was important for NobelClad’s end-to-end supply chain partners to consider how best to maintain Alloy 825’s corrosion-resistant properties at the main manufacturing stages.

VDM Metals manufactured the plates for cladding in Germany. The production process included melting, secondary metallurgical treatment, hot rolling, annealing and surfacing the material. Plates made by VDM Metals pass through stringent quality control protocols. In-process checks and inspections are conducted onsite to ensure full compliance with the required product properties. For this reason, VDM Metals operates its own laboratories to test the exact chemical composition of each alloy, including the alloy’s mechanical properties and corrosion behavior.

ASTM G28 Meth A is the most appropriate corrosion test for Alloy 825. After carrying out heat treatments following manufacturing requirements, VDM cut production plate coupons and conducted the ASTM G28 Meth A tests. Three main manufacturing stages - and the related heat treatments - were considered for coupon preparation:

• Delivery condition
• Head heat treatment simulation
• Head forming at 1,035°C cooling air
• Normalizing plus accelerating cooling at 900°C + water
• Tempering at 650°C cooling air
• Simulated Post-weld Heat Treatment (SPWHT) 3.5 hours at 610°C x 3
• Shell heat treatment simulation
• SPWHT 3.5 hour at 610°C x 3

Upon completion, the corrosion test results confirmed heat treatment settings in vessel manufacturing produced perfect matches to customers’ requirements. The simulated post-welding heat treatment slightly increased corrosion rates but the rates remain far below 0.9 mm/yr. The ratio is similar between annealed condition and after head heat treatment simulation. 

These statistically reliable results confirm the benefit of an end-to-end supply chain in which high-quality suppliers work together to manufacture critical equipment using stringent backed by stringent quality control protocols.

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