The Myth of Chrome White Iron and Hardness
From “chrome white iron is brittle” to “you can’t machine ASTM A532,” you’ll often hear myths when it comes to chrome white iron. But the reality is that ASTM A532 outperforms steel, AR plate and weld overlay in many applications requiring abrasion resistance.
More importantly, it outperforms materials of a similar hardness and often for less money.
In a nutshell - the carbides in the matrix allow chrome white iron to have such exceptional wear life.
Let’s imagine that there are two paved roads. On one road there is aggregate mixed with hard tar, while the other road is simply paved – no aggregate. The road with the aggregate will wear better, as the aggregate will take on most of the repetitive traffic flow, leaving the hard tar intact. To take this analogy into chemistry, the carbides in chrome white iron act much like aggregate does in a paved road. The tar is the matrix holding the aggregate in place as the aggregate takes the wear.
Check out this chart below, courtesy of an article from the National Resource Council which explores the gouging abrasion resistance of materials for oil sands services.
- The gouging wear chart above shows volume loss for chrome white iron (CrMo WI) and AR 600. The chrome white iron is shown at 730BHN while the AR 600 is listed at 552BHN
- The CWI is only 32% harder than the AR 600, but the AR 600 loses almost 2.5X the volume in wear testing. The reason, again, is that the ASTM A532 has carbides, much like the tar in the road has aggregate
Where to Use Chrome White Iron for Best Effect
- Pumps impellers and suction or bearing liners
- Chute liners, apron-feed liners, and gyratory crusher liners
- 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