Material Family

Nickel-Iron-Chromium-Molybdenum-Copper Precipitation-Hardenable Superalloy

A high-strength variant of the 825 family, designed for age-hardening.

Common Supply Conditions

1. Solution Annealed (Soft Condition): For all forming, machining, and welding. 2. Solution Treated & Aged (STA): Supplied in the final high-strength condition for non-welded assemblies.

Most pipe for fabrication is supplied Solution Annealed; final aging is done post-weld/fabrication.

Chemical Composition (Typical wt.%)

Ni: 42.0 - 46.0
Cr: 19.5 - 22.5
Fe: ≥ 22.0 (Balance)
Mo: 2.5 - 3.5
Cu: 1.5 - 3.0
Ti: 1.9 - 2.4
Al: 0.1 - 0.5

Composition similar to 825, but with critical additions of Titanium (Ti) and Aluminum (Al) to form the γ' (Ni₃(Al,Ti)) strengthening precipitates during aging.

Mechanical Properties (Typical)

Solution Annealed (As-Supplied):
• Tensile: 690 - 860 MPa
• Yield: 345 - 550 MPa
• Elongation: 25 - 40%
After Full Aging (Aged):
• Tensile: 965 - 1170 MPa
• Yield: 690 - 860 MPa
• Elongation: 15 - 25%

The dramatic strength increase after aging is the core value, meeting requirements for high-grade OCTG and downhole tools.

Physical Properties

Density: 8.08 g/cm³
Melting Range: 1345 - 1385 °C
Primary Service Range: Up to ~205°C (400°F) for sour service; higher for non-sour applications.

Strength is maintained in the typical downhole temperature range.

Key Performance Attributes

• High Strength & Excellent Sulfide Stress Cracking (SSC) Resistance per NACE MR0175/ISO 15156.
• Excellent chloride stress corrosion cracking (Cl-SCC) and pitting resistance.• Good resistance to sour (H₂S/CO₂/Cl⁻) and slightly oxidizing environments.• Good general corrosion resistance similar to alloy 825.

Engineered specifically for high-stress components in sour oil & gas production where standard CRAs lack sufficient strength.

Key Standards (Pipe)

Seamless Pipe: ASTM B423 / ASME SB-423 can apply for solution annealed material. Specific OCTG specifications (API 5CT/5CRA) are often governing.
Mandatory: Compliance with NACE MR0175/ISO 15156 for sour service.

Often procured as Oil Country Tubular Goods (OCTG) – tubing, casing, coupling stock – to API standards.

Heat Treatment (Aging)

Standard aging: 720°C for 8hrs, furnace cool to 620°C, hold 8hrs, air cool. For Solution Annealed pipe, this is performed after all fabrication/welding is complete.

This two-step aging is essential to develop the full γ' precipitate strengthening and achieve NACE compliance.

Common Sizes & Forms

OD Range: Typically tubing sizes (1.9" to 4.5") and casing sizes (4.5" to 9.625") as per API standards.
Wall Thickness: Various weights per API specifications.
Forms: Primarily Seamless (SMLS).

Used as high-strength, corrosion-resistant tubing, casing, and pup joints in sour wells.

Typical Applications

• Oil & Gas: Sour service production tubing & casing, downhole tool components, wellhead equipment, flowlines.
• Fasteners & Components: Blanks for high-strength bolts, studs, hangers, and valves for corrosive, high-stress service.

The dominant material for critical, high-strength piping in sour (H₂S) service where both strength and environmental cracking resistance are mandatory.