Ni Hard/High Chrome is cast iron with nickel or chromium added to it, making it hard enough to resist abrasion. Wear can come in many forms such as gouges, corrosion, etc. The most reliable way to test its durability is to use it in service.
Microstructure of Type 1 Ni Hard
Type 1 Ni Hard (shown right) consist of continuous white carbides of M3C and islands of the gray Martensite. Again, this is produced in a basic lined cupola, which is the best alloy overall and the most cost-effective.
There is only one heat treatment applied to Type 1 Ni Hard, which is a stress relief treatment at 600 degrees Fahrenheit. With a liquid nitrogen treatment, the as-cast Brinell Hardness Number (BHN) can be raised to 675 from 550 as needed.
Chill casting may be appropriate for increased wear due to grain refining without affecting the hardness. Similarly, a small increase in hardness will result if cast in a permanent mold with heavier sections for increased wear.
Microstructure of Type 4 Ni Hard
Type 4 Ni Hard (shown left) is nearly opposite of Type 1 in that it is continuous grey Martensite and has islands of white M7C3. It also has all the qualities of Type 1.
The difference: Type 4 can be heat treated at 1800 degrees Fahrenheit using a solution of secondary carbides, which raises the BHN to 600. A cupola can be used to produce this as well.