Coefficients of friction are determined empirically. You must specify the other material with which the Incoloy is in contact. Also, surface profiles (smoothness) and conditions (wet, dry, lubricated, etc.) must be considered. Additionally, static (starting from rest) and dynamic (maintaining movement) coefficients are different. If empirical testing is not an option, use coefficient values from similar material pairs listed in various publications (e.g., Machinery's Handbook). A well defined problem is half solved.