Hi Guys
As Michael says, Crobalt is a cast alloy containing 50% cobalt, the other half is made up of tungsten and chromium, it has no iron or steel in it.
Crobalt comes into its own when used on tougher materials such as cast iron and stainless steel, it will work fine on any other materials that you would normally use HSS for but will withstand much higher working temperatures. Coolant is not usually needed unless to improve surface finish.
If you are just doing light turning of mild steel or brass, Crobalt will give the same sort of results as M42 HSS, although the cutting edge will normally last longer on the Crobalt, that's why it was used on repetition lathes in preference to HSS until carbide took over.
There is a video on the Eccentric Engineering website showing a test between Crobalt and a premium brand M42 HSS. The test was done on 304 stainless, and cast iron, the results were pretty emphatic.
The video is on the Crobalt information page, just click the orange Eccentric Engineering ad on the right hand side of this page if you want to have a look.
Crobalt also have an information page here http://www.crobaltusa.com/index.htm
Cheers
Gary
Eccentric Engineering