I think Stellite is a nickel-boron or chromium-boron or chromium-cobalt (or whatever depending on specific grade) material that is sometimes applied as a coating by thermal spray. I think Nickel-boron is a material applied to the substrate by electroless plating (based on a quick google search). It is also a material and deposits a coating of nickel-boron on the substrate. It is the hard and smooth properties of the nickel that give it low friction. Maybe the material is not as analagous to stellite as I thought, but it does appear to be a coating.