The aim of the present book is to study a well known problems in oil and gas industries which are the surface failures of the different types of valves in one side and their high manufacturing cost in the other side. This techno-economic dilemma can have many solutions from the different existing sciences. As tribologists and material scientists, our solution is to replace the valves materials from massive stainless steels into carbon steels with nitrided and optimized stainless steel coatings using thermal spray process and plasma nitriding technique with improved surface properties (hardness, friction, wear resistance and corrosion resistance) and so with lower cost.