VDM® Alloy 2120

VDM® Alloy 2120 MoN has a wide range of applications in the chemical, petrochemical and pharmaceutical industries as well as in energy production and environmental technologies. Typical applications include: components in flue gas desulfurization and waste incineration plants as e.g. scrubbers, raw gas inlets and heat recovery systems, handling of mineral acids like sulfuric acid, hydrochloric acid and acid mixtures even when contaminated with chlorides, acetic acid and acetic anhydride production, production and processing of halogen containing chemicals, equipment for organic synthesizes and fine and specialty chemicals production, components exposed to seawater and to highly concentrated brines, sour gas and geothermal services.

For cold forming the material should be in the annealed condition. VDM® Alloy 2120 MoN has a higher work-hardening rather than austenitic stainless steels. This should be taken into account when selecting forming equipment. Interstage annealing may be necessary with high degrees of cold forming. After cold working with more than 15% deformation solution annealing is required before use.

VDM® Alloy 2120 MoN can be used in many chemical processes with both oxidizing as well as reducing media. The high chromium and molybdenum concentrations make the alloy very resistant to chloride attacks. VDM® Alloy 2120 MoN has a PREN no. of 86 (PREN = %Cr+3.3Mo+30N). In general, the material is superior to other C-alloys in terms of crevice and pitting corrosion. The material possesses outstanding corrosion resistance in reducing acids, such as hydrochloric acid and sulfuric acid. VDM® Alloy 2120 MoN exhibits a good resistance to intercrystalline corrosion according to ASTM G28 method A. Optimum corrosion resistance is only ensured if the material is used in a clean and metallic bright condition.

Machining of VDM® Alloy 2120 should take place in an annealed condition. Because of the considerably elevated tendency toward work hardening in comparison with low-alloy austenitic stainless steels, a low cutting speed and a feed level that is not too high should be selected and the cutting tool should be engaged at all times. An adequate chip depth is important in order to cut below the previously formed strain-hardened zone. Optimum heat dissipation through the use of large quantities of suitable, preferably aqueous, lubricants has considerable influence on a stable machining process.

Solution annealing should take place at temperatures of between 1,150 and 1,185°C (2,102–2,156°F) to achieve optimal properties. The retention time during annealing depends on the semi-finished product thickness. The retention time commences with material temperature equalization; longer times are generally considerably less critical than retention times that are too short. For maximum corrosion resistance, the workpieces must be quickly cooled from the annealing temperature of at least 1,100 to 500°C (2,012 to 932°F) with a cooling rate of >150°C/min (302°F). The material must be placed in a furnace that has been heated up to the maximum annealing temperature before any heat treatment. The cleanliness requirements listed under "Heating" must be observed. For strip product form, the heat treatment can be performed in a continuous furnace at a speed and temperature that is adapted to the strip thickness.

VDM® Alloy 2120 can be hot-formed at a temperature range of between 1,200 and 1,050 °C (2,190 and 1,922 °F) with subsequent rapid cooling down in water or in air. For heating up, workpieces should be placed in a furnace that has been heated up to the maximum hot-forming temperature (solution annealing temperature). The workpieces should be retained in the furnace for around 60 minutes per 100 mm of thickness once the furnace has reached its temperature again. After this, they should be removed from the furnace immediately and formed within the temperature range stated above, with reheating necessary once the temperature reaches 1,050°C (1,922°F). Solution annealing after hot forming is recommended for the achievement of optimal properties and maximum corrosion resistance.

VDM® Alloy 2120 MoN has a face-centered cubic structure. In the temperature range from 600 to 1140°C, intermetallic phases may form in the event of longer exposure times or too slow cooling down. In addition, carbides can precipitate on the grain boundaries, which reduce resistance against intercrystalline corrosion.

Care should be taken that the work is performed with a deliberately chosen, low heat input. The stringer bead technique is recommended. The interpass temperature should not exceed 150°C (302°F). The welding parameters should be monitored as a matter of principle.