Turbocharger compressor wheels having a bi-layered coating and methods for manufacutring the same

A method for manufacturing a bi-layer coated compressor wheel for a turbocharger, comprising:

• providing or obtaining a substrate compressor wheel, wherein the substrate compressor wheel comprises:
• a hub portion defining a rotational axis, and
• a plurality of blades extending radially outward from the hub portion, wherein each blade of the plurality of blades comprises a leading edge, the leading edges of each blade of the plurality of blades forming an inducer portion of the substrate compressor wheel, wherein each blade of the plurality of blades comprises a trailing edge, the trailing edges of each blade of the plurality of blades forming an exducer portion of the substrate compressor wheel, the inducer portion being positioned longitudinally forward from the exducer portion along a rotational axis with respect to a flow of air along the substrate compressor wheel,
• wherein the hub portion and the plurality of blades comprise a substrate metal;
• forming on the substrate metal of the hub portion and the plurality of blades a first coating layer comprising electroless nickel-phosphorous, wherein forming the first coating layer comprises immersing the substrate compressor wheel in an electroless nickel-phosphorous plating bath comprising nickel cations and phosphorous oxide anions;
• and
• forming on the first coating layer a second coating layer comprising hard chrome, wherein the second coating layer has a thickness that is greatest at the inducer portion, the thickness of the second coating layer decreasing in a tapering manner rearward towards the exducer portion such that the thickness of the second coating layer is zero microns at or longitudinally forward of the trailing edges of each blade of the plurality of blades, and wherein forming the second coating layer comprises immersing the compressor wheel coated with the first coating layer in a chromium plating bath comprising an oxide of chromium and an acid of sulfur, and applying an electric current using an anode and a cathode, the compressor wheel coated with the first coating layer functioning as the cathode, wherein the inducer portion is oriented facing the anode in the chromium plating bath.