Cold spraying a coating onto a rotor in a downhole motor assembly

Systems and methods for cold-spraying coatings on rotors in motor assemblies for improving reliability of motor assembly use downhole in wellbores is provided. For example, a motor assembly can include a stator positioned downhole in a wellbore and rotor coupled to the wellbore. The rotor can include a base material and a first coating deposited onto the base material via cold spraying for reducing damage to the rotor. The first coating may include sprayed particles that have a melting point temperature that is higher than a temperature of a gas used in the cold spraying. In some examples, the rotor may include a second coating deposited onto the first coating via cold spraying, high velocity oxygen fuel coating, or high velocity air fuel. The first coating may have a first hardness that is less than a second hardness of the second coating.