CT6945 Hastelloy G3 Wire

Hastelloy G3 Wires Description

Hastelloy G3 wires exhibit a microstructure produced by heavy cold working. The microstructure contains elongated austenitic grains aligned along the wire axis. Cold working has resulted in high dislocation densities (exceeding 1 000 000 000 000 000 m⁻²) and a <111> crystallographic texture. The wires demonstrate tensile strengths of 1 000–1 200 MPa and elongation between 15% and 20%. The material shows mechanical anisotropy. Axial ductility remains above 15% fracture strain. Transverse impact toughness is lower due to grain boundary alignment.

Corrosion resistance originates from a passive film formed mainly by chromium and molybdenum oxides. This film exhibits high electrochemical stability in reducing acid and chloride‐containing environments. The critical pitting temperature is above 85°C in ferric chloride solutions. The alloy resists stress corrosion cracking in sour brines at temperatures up to 150°C. A surface finish (Ra ≤0.8 μm) reduces pit initiation. Repassivation kinetics reduce the propagation of localised attack.

At temperatures below 400°C, the cold‐worked structure remains metastable and retains over 85% of its strength after extended exposure. Recrystallisation starts at 600°C and gradually restores annealled properties. Phase stability persists below 650°C with little intermetallic formation. Electrical resistivity increases linearly with the degree of cold work and reaches 1.18 μΩ·m at maximum hardness. A ductile‐to‐brittle transition occurs at around –50°C in the transverse direction due to texture‐related constraints. However, longitudinal specimens remain ductile at cryogenic temperatures. Degradation results from slip‐induced rupture of the passive film in chloride environments. Molybdenum‐enriched oxides help to restore the film.

Hastelloy G3 Wires Applications

Hastelloy G3 wires are used in various industries that require high corrosion resistance and consistent mechanical performance. In chemical processing, the wires are used to manufacture submerged arc welding electrodes for reactors that process sulphuric and phosphoric acids. They also form springs for acid vapour scrubbers used with HCl/HF mixtures and thermowell sheaths for instruments in chloride‐rich slurries. In the oil and gas sector, the wires serve for sour gas well screens in H₂S/CO₂/chloride mixtures and as braided armour for downhole tools in acidifying operations. They are also used for valve trim springs in aggressive hydrocarbon environments.

Pollution control applications include cathodic cage structures in flue gas desulphurisation systems and filter meshes for sulphuric acid regeneration plants. Emerging applications use the wires’ cold‐worked strength (1 000–1 200 MPa) and a surface finish (Ra ≤0.8 μm) for anode baskets in zinc/cobalt electrowinning. They are used in heat exchanger internals in geothermal brines prone to silica scaling, and as wires for nuclear waste encapsulation that resist nitric acid and nitrate corrosion. The wires sustain dimensional stability under high vibration and thermal cycling. They are approved for continuous operation at 400°C with periodic exposure to 600°C. Their performance is based on measured resistance to localised corrosion in acidic and chloride environments, and on the retention of mechanical properties in severe thermochemical conditions.

Hastelloy G3 Wires Packaging

Our products are packed in customised cartons of various sizes according to the material dimensions. Smaller items are packed in PP boxes, while larger items are placed in custom wooden crates. We adhere to packaging specifications and use appropriate cushioning materials to protect the items during transport.

Packaging: Carton, Wooden Box, or Customized.

Please review the packaging details provided for your reference.

Manufacturing Process

1.       Testing Method

(1)    Chemical Composition Analysis was performed using techniques such as GDMS or XRF. This analysis confirmed compliance with purity requirements.

(2)    Mechanical Properties Testing includes tensile strength, yield strength and elongation tests to assess material performance.

(3)    Dimensional Inspection measures thickness, width and length to verify adherence to specified tolerances.

(4)    Surface Quality Inspection checks for defects such as scratches, cracks or inclusions using visual and ultrasonic examination.

(5)    Hardness Testing determines material hardness to confirm uniformity and mechanical reliability.

Please refer to the SAM testing procedures for further information.

Hastelloy G3 Wires FAQs

Q1. How does the alloy maintain corrosion resistance in sulphuric acid environments above 60°C, where standard stainless steels do not perform adequately?

Hastelloy G3’s chromium–molybdenum–copper composition (Cr-22%, Mo-6.5%, Cu-2%) produces stable passivation through Cr/Mo‐rich oxide layers. This passivation withstands sulphuric acid concentrations of up to 50% at temperatures of up to 90°C. In contrast, 316L stainless steel undergoes surface thinning of more than 5 mm per year above 60°C due to breakdown of passive films that rely solely on chromium.

Q2. What maximum chloride concentration and temperature limit prevent stress corrosion cracking in sour gas service?

The alloy maintains resistance to stress corrosion cracking with chloride levels of up to 150 000 ppm, H₂S partial pressures of up to 3.5 bar and temperatures of up to 150°C. Beyond these values, depletion of molybdenum at grain boundaries may initiate cracking. A solution annealing treatment at 1120°C can reduce this risk.

Q3. Does cold working affect corrosion performance in welded assemblies?

Cold work exceeding a 15% reduction results in a critical pitting temperature that is 20–30% lower in chloride environments. Post‐weld solution annealing at 1100°C ±15°C restores a homogeneous microstructure and yields corrosion resistance equivalent to that of the base metal.

Related Information

1.       Common Preparation Methods

Hastelloy G3 wires are manufactured via a multi‐stage thermomechanical process. The procedure begins with vacuum induction melting (VIM) of high‐purity raw materials. These include electrolytic nickel, chromium, molybdenum and copper. The process occurs under an inert atmosphere to achieve precise compositional control.

The molten alloy undergoes secondary refining using vacuum arc remelting (VAR). This step reduces interstitial elements (oxygen ≤30 ppm, nitrogen ≤100 ppm) and eliminates macrosegregation.

The ingot is homogenised at 1200–1250°C for 8–12 hours to dissolve eutectic phases. It then undergoes hot forging within the γ‐austenite stability range (1050–1150°C) with a reduction ratio of at least 4:1 to disrupt the as‐cast structure.

Hot rolling is performed at 980–1040°C. This process reduces the cross‐section to form intermediate billets with diameters between 20 and 50 mm. Controlled strain rates (0.1–1 s⁻¹) are used to prevent hot cracking due to copper‐induced embrittlement.

Subsequently, the material undergoes solution annealing at 1120±10°C for 1 hour per 25 mm of thickness. It is then rapidly water quenched to retain a supersaturated solid solution. Wire production starts by drawing hot‐rolled rods through progressively smaller diamond dies at room temperature. Each pass achieves a cross‐sectional reduction of 30–40%. Intermediate soft annealing at 1080°C is carried out after every 30–40% cumulative reduction to restore ductility and prevent work‐hardening fractures. Final cold drawing stages involve light reductions of 10–15% to attain target diameters between 0.5 and 10 mm. The process increases tensile strength to between 1 000 and 1 200 MPa. Microstructural control maintains a grain size between ASTM values 5 and 7 (20–50 μm). Exposure to 600–900°C in thermal cycles is limited to under 15 minutes, which prevents σ‐phase nucleation. Surface finishing is achieved by electrochemical polishing to a roughness of Ra ≤0.8 μm. The material is then pickled in HNO₃/HF solutions to remove scale without depleting chromium. Quality verification includes eddy current testing for defects larger than 50 μm, continuous ultrasonic inspection for internal discontinuities and electrochemical validation of repassivation kinetics in accordance with ASTM G61.