Why Chrome White Iron Outperforms AR 400

In this blog post Penticton Foundry discussed a report from a local mine in British Columbia.  The mine had noted the superior wear performance of chrome white iron as compared to AR 400 plate.

The question is – why is chrome white iron superior to AR 400 plate?  The answer lies in both its microstructure and macrostructure.

Microstructure
AR 400 is made up of only martensite.  In contrast, ASTM A532 or high chrome white iron is made up of 60% martensite.  The remainder of the microstructure of chrome white iron is comprised of carbides which are over 4x harder than martensite.

Why is this important?
These carbides increase the abrasion resistance of chrome white iron by a factor of 10 or more.  The result of this increase is superior wear performance by chrome white iron.

Macrostructure
Chrome white iron also has several macrostructure advantages:

• Any thickness can be cast, whereas AR 400 plate is limited
• Any shape can be cast (compound angles, radii, etc.) vs. AR 400 plate which only comes as a plate
• When AR plate is burned to shape it develops a heat affected zone. The changes in the heat affected zone cause stresses. Theses stresses can lead to cracking and lower strength in the area
• Holes can be cast into ASTM A532. Compare this to AR 400 plate which has to have holes machined or burned in – increasing the price and lead time of AR 400 plate

There are several advantages both from a microstructure and macrostructure perspective that allow chrome white iron to outperform AR 400 plate in a variety of applications.

A Few Applications for Chrome White Iron:

• Pump impellers and suction or bearing liners are some of the most common uses for chrome white iron.
• Chute liners, apron-feed liners, and gyratory crusher liners are very common uses in the mining industry.
• Recycling-plant parts like blow bars, anvils and throw shoes are best made in high chrome white iron.
• Hydro-transport parts like laterals, wyes, reducers and elbows can be made with our chrome white iron.

These are just some of the products that can be made out of chrome white iron.  For more information on chrome white iron, check out our abrasion resistant alloys page.