A screw machine (10) has a rotor housing (12) defining overlapping bores (12-1,12-2). Female rotor (14) is located in bore (12-1) and male rotor (16) is located in bore (12-2). A wear resistant coating is deposited on the tips (14-1, 16-1) of the rotors. A conformable coating is deposited on the valleys (14-2, 16-2) of the rotors. A conformable coating is deposited on the surface of the bores coacting with the rotors.
