Incoloy Alloys: Grades, Properties, Pipes, Tubes & Fittings

INCOLOY is a registered trademark of Special Metals Corporation. Sagiant Piping Industries is an independent supplier and stockist, not the alloy producer. Identify the exact UNS number, specification edition and condition on enquiry; alloy 825 is INCOLOY (iron-nickel-chromium) and is distinct from the nickel-based Inconel family.

Producer reference limits; “bal” denotes balance and is not a fixed value; a dash means not separately specified, not zero. Carbon and grain-size control distinguish 800 / 800H / 800HT and belong to the ordered specification. These are not independently verified current limits for every product specification — the purchase specification edition and heat/product certificate control acceptance.

“Core” grades have completed technical records; “Reference” names are established in manufacturer literature and are quoted as reference-only until form, specification and availability are confirmed — a listing is not a stock or availability statement. Aliases (20/020, 28/028) are normalised, not duplicated. UNS cross-references are not substitution approvals. Do not confuse INCONEL 600/625/718 (nickel-based) with the INCOLOY family; 901 (NIMONIC) and 902 (NI-SPAN-C) are separate families.

Indicative requirements shown against the referenced ASTM product specification; the exact grade, product form, size interval, heat treatment, orientation and test method must be confirmed on the certificate. Specification minima, specification maxima and typical producer measurements are different datasets and are kept separate. 800H and 800HT are combined here for space but are separate certified grades. Elevated-temperature tensile, creep/stress-rupture (800H/800HT), hardness, impact and fatigue data are taken from the ordered specification; design-code allowable stresses are not derived from tensile strength.

Producer reference densities near ambient. Melting ranges are not service temperatures. Use the grade-specific density in the weight calculator, not one generic value. Young’s and shear modulus, Poisson’s ratio, specific heat, thermal conductivity, mean thermal-expansion coefficient (with its interval), electrical resistivity and magnetic permeability are provided per grade on enquiry with temperature/condition. Do not treat the family as “essentially non-magnetic” — controlled-expansion grade 909F has a ferromagnetic-to-paramagnetic transition. Controlled-expansion grades (903/907/909) need their expansion curve and heat-treatment dependence.

A routing matrix for specification review, not a universal certification. Where invoked, general-requirement standards B829 (seamless tubular), B751 (welded tube), B775 (welded pipe) and B906 (flat) also apply. ASTM and ASME SB adoption editions are not automatically identical; for European purchasing record the applicable EN product standard, not merely “EN”. Construction codes (B31.3 / B31.1 / BPVC) define pressure design; a material standard does not by itself establish pressure suitability.

Availability is confirmed per enquiry with stocked / sourced / made-to-order status — the ranges below are indicative, not a statement that every grade is held in every size, schedule and condition.

Class 2500 is a flange pressure class, not “2500 psi”, and B16.5 Class 2500 extends only to NPS 12. STD/XS do not always equal Sch 40/80, and 40S/80S differ from 40/80 at some sizes. Keep dimensional standards (B36.10 / B36.19) separate from material specifications. Finished fasteners need a component/fastener acceptance basis; a bar specification alone is not sufficient. See the schedule chart and weight calculator.

• 825 / 020: aqueous corrosion in sulphuric and phosphoric acids, with chloride pitting and stress-corrosion-cracking resistance from Ni, Mo and Cu. Resistance depends on acid concentration, temperature, aeration, contaminants and condition — not immunity.
• 825 temperature: exposure above approximately 540°C can cause phase changes that reduce ductility and impact toughness — this is a metallurgical caution, not a universal maximum service temperature.
• 800H / 800HT: high-temperature creep and stress-rupture strength; oxidation resistance is atmosphere-dependent (carburisation, sulfidation, nitridation). A single “~1100°C” figure is not a pressure-design temperature — separate time/stress-dependent creep from oxidation limits.
• Corrosion review covers general corrosion, pitting, crevice attack, chloride SCC, intergranular attack/sensitisation and, where applicable, sour-service cracking. Numerical rates require solution, concentration, temperature, aeration, velocity, time and method.
• Sour service: ISO 15156-3 / NACE MR0175 qualification depends on the exact alloy, condition, hardness, processing and the H₂S / chloride / pH / temperature envelope. Chemistry identification (MTC / PMI) alone cannot establish it.