Wheels having a bi-layered coating and methods for making the same

Abstract

A wheel includes a hub portion configured to rotate about a rotational axis. A plurality of blades extends radially outward from the hub portion. Each blade of the plurality of blades includes a leading edge and a trailing edge. The hub portion and the plurality of blades include a substrate metal. The substrate metal of the plurality of blades has coated directly thereon a first coating layer including electroless nickel-phosphorous having a phosphorous content of about 4 wt. % or greater. The first coating layer has coated directly thereon overlying the plurality of blades a second coating layer including electroless nickel-phosphorous poly-alloy having a phosphorous content that is lower than the phosphorous content of the first coating layer. The second coating layer is a functional coating layer with enhanced erosion resistance.

1 . A wheel comprising:
 a hub portion configured to rotate about 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 and a trailing edge,   wherein the hub portion and the plurality of blades comprise a substrate metal,   wherein the substrate metal of the plurality of blades has coated directly thereon a first coating layer comprising electroless nickel-phosphorous having a phosphorous content of about 4 wt. % or greater, and   wherein the first coating layer has coated directly thereon overlying the plurality of blades a second coating layer comprising electroless nickel-phosphorous poly-alloy having a phosphorous content that is lower than the phosphorous content of the first coating layer, wherein the second coating layer is a functional coating layer with enhanced erosion resistance.   
     
     
         2 . The wheel of  claim 1 , wherein the first coating layer comprises the electroless nickel-phosphorous having the phosphorous content of about 4 to about 9 wt. % and a nickel content of about 91 to about 96 wt. %. 
     
     
         3 . The wheel of  claim 1 , wherein the second coating layer comprises the electroless nickel-phosphorous having the phosphorous content of about 1 to about 1.5 wt. % and a nickel content of about 97 to about 98 wt. %. 
     
     
         4 . The wheel of  claim 1 , wherein the second coating layer comprises the electroless nickel-phosphorous having a cobalt content of about 0.5 to about 1.5 wt. %. 
     
     
         5 . The wheel of  claim 1 , wherein the second coating layer comprises the electroless nickel-phosphorous having a tungsten content of about 0.05 to about 0.6 wt. %. 
     
     
         6 . The wheel of  claim 1 , wherein the first coating layer has a thickness of about 1 to about 5 microns. 
     
     
         7 . The wheel of  claim 1 , wherein the second coating layer has a thickness of about 20 to about 25 microns. 
     
     
         8 . The wheel of  claim 1 , wherein the first and second coating layers extend overlaying the substrate metal of the hub portion. 
     
     
         9 . The wheel of  claim 1 , wherein the substrate metal comprises aluminum or an alloy thereof. 
     
     
         10 . The wheel of  claim 1 , wherein the second coating layer has a hardness of about 800 HV or greater. 
     
     
         11 . The wheel of  claim 10 , wherein the hardness of the second coating layer is from about 800 HV to about 1000 HV. 
     
     
         12 . The wheel of  claim 1 , wherein the wheel is configured as a turbocharger compressor wheel or a fuel cell turbine wheel. 
     
     
         13 . A wheel comprising:
 a hub portion configured to rotate about 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 and a trailing edge,   wherein the hub portion and the plurality of blades comprise a substrate metal that comprises aluminum or an alloy thereof,   wherein the substrate metal of the plurality of blades has coated directly thereon a first coating layer comprising electroless nickel-phosphorous having a phosphorous content of about 4 wt. % or greater, and   wherein the first coating layer has coated directly thereon overlying the plurality of blades a second coating layer comprising electroless nickel-phosphorous poly-alloy having a phosphorous content of about 1 to about 1.5 wt. %, a cobalt content of about 0.5 to about 1.5 wt. %, and a tungsten content of about 0.05 to about 0.6 wt. %, wherein the second coating layer is a functional coating layer with enhanced erosion resistance.   
     
     
         14 . A method for making a wheel, the method comprising:
 providing a substrate wheel that comprises:   a hub portion configured to rotate about 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 and a trailing edge,   wherein the hub portion and the plurality of blades comprise a substrate metal that comprises aluminum or an alloy thereof;   forming on the substrate metal a first coating layer comprising electroless nickel-phosphorous having a phosphorous content of about 4 wt. % or greater, wherein forming the first coating layer comprises immersing the substrate wheel in a first electroless nickel-phosphorous plating bath comprising nickel cations and phosphorous oxide anions; and   forming on the first coating layer a second coating layer comprising electroless nickel-phosphorous poly-alloy having a phosphorous content that is lower than the phosphorous content of the first coating layer on the first coating layer, wherein forming the second coating layer comprises immersing the substrate wheel with the first coating layer in a second electroless nickel-phosphorous plating bath comprising nickel cations, phosphorous oxide anions and other alloy ions and subsequently, exposing the substrate wheel including the first and second coating layers to a heat treatment process to thereby increase a hardness of the second coating layer as a functional coating layer with enhanced erosion resistance.   
     
     
         15 . The method of  claim 14 , wherein exposing the substrate wheel including the first and second coating layers to the heat treatment process includes exposing the substrate wheel including the first and second coating layers to a temperature of about 175° C. to about 250° C. for a time of about 0.5 to about 4 hours. 
     
     
         16 . The method of  claim 15 , wherein the treatment process includes exposing the substrate wheel including the first and second coating layers to the temperature of about 195° C. to about 240° C. for a time of about 1 to about 4 hours. 
     
     
         17 . The method of  claim 14 , wherein forming the first coating comprises immersing the substrate wheel in the first electroless nickel-phosphorous plating bath comprising nickel cations and phosphorous oxide anions at a pH of about 4 to about 5. 
     
     
         18 . The method of  claim 17 , wherein forming the first coating comprises immersing the substrate wheel in the first electroless nickel-phosphorous plating bath for a time of about 20 to about 40 minutes. 
     
     
         19 . The method of  claim 14 , wherein forming the second coating comprises immersing the substrate wheel with the first coating layer disposed thereon in the second electroless nickel-phosphorous plating bath comprising nickel cations, phosphorous oxide anions, cobalt cations, and tungsten cations at a pH of about 6 to about 9. 
     
     
         20 . The method of  claim 14 , wherein forming the second coating comprises immersing the substrate wheel with the first coating layer disposed thereon in the second electroless nickel-phosphorous plating bath for a time of about 130 to about 170 minutes.