Low coefficient of expansion rotors for blowers

A blower assembly comprising:

• a blower chamber including a gas inlet for allowing gas to enter the blower chamber and a gas outlet to allow gas to exit the blower chamber;
• a first rotor positioned within the blower chamber and adapted for rotation therein, the first rotor including a first shaft and at least two lobes having an outer surface that defines a first lobe profile;
• and
• a second rotor positioned within the blower chamber and adapted for rotation therein, the second rotor including a second shaft and at least two lobes having an outer surface that defines a second lobe profile,
• wherein the blower chamber includes opposing transverse plates through which shafts supporting the first and second rotors extend, and
• wherein the first and second rotors formed from metal having a coefficient of thermal expansion from 1 (10−6 in/in*K) to 13 (10−6 in/in*K) and including at least 50% iron, 20% to 35% nickel, and 10% to 25% cobalt, wherein an inner surface of the blower chamber includes a coating including at least one of an abradable coating or a formable coating, and wherein a portion of the coating has a surface roughness from 125 Ra to 1000 Ra.