Low Alloy Steel shaft , Gear & Pinion Wheel materials in compressors and in other equipments are often subjected to Case Hardening Surface Engineering like Carburizing , Nitriding , Cyaniding etc. Nitriding usually renders relatively higher hardness & wear resiance than Carburising. ( 1 ) Now so far as service performance w.r.t. Fatigue is concerned between Carburizing and Nitriding which one should be preferred technically ? ( 2 ) W.r.t. a Cost / Benefit analysis under long term perfoamnce perspective between Carburising and Nitriding which one should be preferred ? An opinion is requested. regards DM