High-chrome white iron and Ni-hard castings for abrasion

High-chrome white iron and Ni-hard are abrasion-resistant white cast irons covered by ASTM A532. Ni-hard is the nickel-chromium Class I family. High-chrome irons are Class II (chromium-molybdenum) and Class III (25% chromium). They are used for mill liners, grinding parts, crusher parts, slurry pump parts and grate bars.

Published 17 Oct 2026 · Updated 17 Oct 2026 · Ni-Chrome Alloy Castings

Enquire about wear irons Request the full datasheet →

What are high-chrome white iron and Ni-hard?

They are white cast irons alloyed to resist abrasive wear, covered by ASTM A532. Carbon in these irons forms hard carbides instead of graphite, and the alloying makes the carbides harder and the metal around them stronger. The result is a casting that outlasts plain steel in grinding, crushing and sliding abrasion, at the cost of toughness. Ni-hard is the nickel-chromium family, A532 Class I. High-chrome irons are Class II and Class III.

ASTM A532 excludes simple and low-alloy white irons. It requires heat treatment, and the castings are supplied hardened and stress-relieved, or softened for machining and hardened after.

What are the ASTM A532 classes?

A532 groups the irons into three classes and eight types:

Class I, types A to D: nickel-chromium irons, the Ni-hard family. Type D, often sold as Ni-hard 4, carries the most chromium of the four.
Class II, types A, B and D: chromium-molybdenum irons. Type B, the one most often ordered, carries 14 to 18% chromium.
Class III, type A: the 25% chromium iron.

The class and type are part of the specification. "High chrome" on a drawing is not enough to cast to, so ask which class and type are meant.

What is the composition of the common A532 grades?

The three types below are the ones most often ordered. Ranges are in weight percent; iron is the balance.

Element	Class I type D (Ni-hard 4)	Class II type B	Class III type A
Carbon	2.5 to 3.6	2.0 to 3.3	2.0 to 3.3
Chromium	7.0 to 11.0	14.0 to 18.0	23.0 to 30.0
Nickel	4.5 to 7.0	2.5 max	2.5 max
Molybdenum	1.5 max	3.0 max	3.0 max
Copper	not specified	1.2 max	1.2 max
Manganese	2.0 max	2.0 max	2.0 max
Silicon	2.0 max	1.5 max	1.5 max

Sources: ASTM A532 ranges as reproduced in a published pump-maker materials sheet (Wilfley) and, for Class I type D carbon and chromium, Total Materia. Phosphorus and sulphur limits differ by type. The edition named on your purchase order governs.

Total Materia lists a minimum hardness of 500 HB for Class I type D in the hardened condition. Hardness in the high-chrome classes depends on heat treatment and is agreed on the order.

Where are wear irons used?

Mill liners, lifter bars and grinding segments in ball, rod and vertical roller mills.
Grinding rolls, bowls, tables and bull rings in coal and cement mills.
Crusher parts: hammers, impact blow bars and liners where the impact is moderate.
Pump parts for slurry: casings, impellers and throat bushes.
Grate bars for sinter machines, where high-chromium iron is a common choice. A study of a high-chromium iron grate bar found it protected by iron and chromium oxide films below about 800 °C.
Chutes, wear plates and liner tiles for ore, coal and clinker handling.

When should you choose Ni-hard over high-chrome iron?

Choose high-chrome iron for most new wear parts. The chromium carbides in Class II and III irons are harder than the iron carbides in the Ni-hard grades, and the higher chromium gives some resistance to wet corrosion, which matters in slurry. Class III, with 23 to 30% chromium, is a common pick for slurry pumps and wet grinding.

Ni-hard still has its place. It is the established grade for many mill and crusher parts, it is simple to specify, and plants replacing like for like often stay with it.

Where heavy impact dominates, as in jaw plates and primary crusher liners, neither is the right answer. Austenitic manganese steel work-hardens under impact and does not shatter. See the manganese steel row in the grade reference.

How do wear-iron castings fail?

Wear-through. The expected end of life. The softer matrix wears first and the carbides stand proud until they break out.
Cracking and spalling under impact. These irons have little ductility. A liner that sees more impact than abrasion, or one that is bolted down unevenly, will crack before it wears.
Heat-checking in parts that run hot and are cooled suddenly, such as grate bars.
Corrosion-assisted wear in acidic or saline slurry, where the low-chrome grades lose metal faster than abrasion alone would explain.

What should an RFQ for wear-iron castings include?

The standard, class and type, such as ASTM A532 Class III type A, or IS 4771, or the grade on the old drawing.
The hardness you need and where it is to be measured.
The drawing, quantity and machining. These irons are machined only in the softened condition or by grinding, so mark which faces matter.
The service: what is being ground or carried, wet or dry, and how much impact.
The life of the current part and how it ended.

Our guide to getting a quote lists the rest.

Enquire about wear irons Request the full datasheet →

Wear iron questions

Is Ni-hard the same as high-chrome iron?

No. Ni-hard is ASTM A532 Class I, a nickel-chromium white iron. High-chrome iron is Class II or III, with much more chromium and harder chromium carbides. Both are white irons for abrasion.

Can wear-iron castings be machined?

Only with difficulty in the hardened state. Holes and critical faces are usually machined in the softened condition before hardening, or ground afterwards. Tell us which faces need finishing when you send the drawing.

What is IS 4771?

The Indian standard for abrasion-resistant white irons. Many Indian mill and crusher drawings name it instead of ASTM A532. We cast to either; send the standard and grade your drawing uses.