Ni-Resist castings: austenitic iron types, properties and uses

Ni-Resist is the common name for austenitic cast irons: irons alloyed with about 13 to 37% nickel, plus chromium, copper or silicon, so the matrix stays austenitic like stainless steel while the graphite stays in the iron. Flake-graphite types are specified in ASTM A436 and spheroidal-graphite (ductile) types in ASTM A439. They are used for pump and valve parts in seawater and mild chemicals, and for exhaust and turbocharger parts that run hot.

Published 15 Nov 2026 · Updated 15 Nov 2026 · Ni-Chrome Alloy Castings

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What is Ni-Resist?

Ordinary grey and ductile irons have a ferrite or pearlite matrix that rusts, scales and grows at temperature. Adding enough nickel turns the matrix austenitic. The result keeps what makes cast iron easy to work with, good fluidity, machinability and damping from the graphite, and gains corrosion, heat and erosion resistance well beyond plain iron. Ni-Resist is not to be confused with Ni-hard, which is a hard white iron for abrasion with a few percent nickel.

Two families exist, and the graphite shape decides which:

Flake graphite, ASTM A436 ("austenitic gray iron"): Types 1, 1b, 2, 2b, 3, 4, 5 and 6. Easier to cast, better damping, lower strength and almost no ductility.
Spheroidal graphite, ASTM A439 ("austenitic ductile iron"): Types D-2, D-2B, D-2C, D-3, D-3A, D-4, D-5, D-5B and D-5S. The graphite is nodular, so tensile strength roughly doubles and the metal has real elongation.

What is the composition of the common Ni-Resist types?

The four types buyers ask for most are below, in weight percent.

Element	D-2 (A439)	D-5S (A439)
Nickel	18.0 to 22.0	34.0 to 37.0
Chromium	about 1.75 to 2.75	1.75 to 2.25
Copper	-	-
Silicon	1.5 to 3.0	4.9 to 5.5
Carbon	3.0 max	2.3 max
Manganese	about 0.7 to 1.25	1.0 max
UNS	F43000	-
Graphite	Spheroidal	Spheroidal

Sources: ASTM A436 and A439 ranges as compiled by MakeItFrom, cross-checked against ASTM A436 table extracts for nickel and copper. Sulphur and phosphorus limits are omitted. Published sources disagree slightly on D-2 manganese (0.70 to 1.0 in the Nickel Institute guide, up to 1.25 elsewhere) and chromium (up to 2.5 or 2.75), so the D-2 figures are shown as approximate. Current editions are ASTM A436-24 and A439/A439M-18 (reapproved 2022); the edition on your purchase order governs.

The differences are deliberate. Type 1 carries copper, which helps in some acids. Type 2 drops the copper and raises nickel, which suits caustic service and duty where copper is unwanted. D-5S adds about 5% silicon to the 35% nickel base, which gives the oxidation and growth resistance that hot exhaust parts need.

What are the equivalents of Ni-Resist?

Type 1: BS 3468 F1, AFNOR FGL Ni15 Cu6 Cr2, ISO 2892 designation L-NiCuCr 15 6 2.
Type 2: BS 3468 F2, AFNOR FGL Ni20 Cr2, L-NiCr 20 2.
D-2: BS 3468 S2, AFNOR FGS Ni20 Cr2, S-NiCr 20 2.
D-5S: BS 3468 S5S, AFNOR FGS Ni35 Si5 Cr2.

"Ni-Resist" itself is a trade name. Order by ASTM type, or by the EN or ISO designation if your drawing uses one, and state which you accept as equivalent.

What properties does Ni-Resist have?

The flake types are modest in strength: BS 3468 gives tensile ranges of roughly 170 to 240 MPa. The ductile A439 types are much stronger and tougher because the graphite is nodular. Take specification minimums from the standard named on your drawing.

Thermal expansion rises and falls with nickel content: the 35% nickel types (Type 5 and D-5) have the lowest expansion in the family, and the 15 to 22% nickel types expand more, so allow for it when Ni-Resist parts are bolted to iron or steel and run hot. Ask for the coefficient of the specific type. All of them are soft enough to machine like grey or ductile iron.

Where is Ni-Resist used?

Pumps and valves in seawater and brine: pump casings, impellers, diffusers and valve bodies, where plain iron would corrode and stainless or bronze would cost more. Flake and ductile types are both used; D-2 is chosen when the part needs toughness.
Mild acids, alkalis and process water: the A436 types resist dilute acids, alkalis and seawater far better than plain iron. Type 2 is preferred over Type 1 for caustic.
Exhaust and turbocharger parts: D-5S was developed as a castable austenitic iron for turbocharger housings and exhaust manifolds, where it resists oxidation and growth at high temperature.
Wear with corrosion: piston-ring carriers, valve guides and pump wear rings, where the part must resist wear and corrosion together.
Sour gas and oilfield service: some A439 types are used in hydrogen-sulphide service, subject to the purchaser's sour-service rules.

How do you choose between Ni-Resist types?

Flake or ductile. If the part sees impact, pressure, bolting loads or thermal shock, choose an A439 ductile type. Choose an A436 flake type where strength demands are modest and damping, castability or machinability lead.
Copper or not. Type 1 (with copper) for general corrosion; Type 2 or D-2 (copper-free) for caustic and where copper contamination matters.
Temperature. For hot exhaust and furnace duty, the high-silicon D-5S. For low thermal expansion, the 35% nickel types (Type 5, D-5) are used.
Against the alternatives. If Ni-Resist is not enough for the chloride level or temperature, the next step is usually CF8M or a duplex stainless, then a nickel alloy such as M35-1 or CW-6MC.

Which casting route suits Ni-Resist?

Ni-Resist is cast in sand moulds like grey and ductile iron, and the ductile types need a magnesium treatment to form spheroidal graphite. Round parts such as sleeves, liners and rings can be cast centrifugally. Ductile types are often stress relieved after casting.

We cast the flake-graphite Ni-Resist types to ASTM A436, in sand moulds and centrifugally.

What should an RFQ for Ni-Resist castings include?

The standard and type, for example ASTM A439 D-2 or A436 Type 1, or the EN or BS designation on your drawing.
The drawing with tolerances, machining and finished weight if known.
Service: the fluid, its chloride content and temperature, or the exhaust gas temperature for hot parts.
Heat treatment, if any, such as stress relief.
Testing: chemistry and tensile certificates, hardness, graphite form (nodularity) for ductile types, pressure test for pump and valve bodies, radiography or penetrant if required, and third-party inspection.
Quantity and delivery needs.

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Ni-Resist questions

Is Ni-Resist the same as Ni-hard?

No. Ni-Resist is an austenitic iron with 13 to 37% nickel, made for corrosion and heat. Ni-hard is a white iron with about 4% nickel, made hard for abrasion, covered by ASTM A532 Class I.

What is the difference between ASTM A436 and A439?

Graphite shape. A436 covers austenitic grey iron with flake graphite. A439 covers austenitic ductile iron with spheroidal graphite, which is stronger and tougher.

What is Ni-Resist D-5S used for?

Mainly turbocharger housings and exhaust manifolds. Its 34 to 37% nickel and about 5% silicon resist oxidation and growth at high temperature.

Is Ni-Resist good in seawater?

It is widely used for seawater pump and valve parts and resists seawater far better than plain cast iron. For the most aggressive chloride service, stainless or nickel alloys are the step up.