Bi-layered Coating for Turbocharger Compressor Wheels

The patent applies composite materials by coating the aluminum compressor wheel with a bi-layered structure: electroless nickel-phosphorous base layer followed by hard chrome top layer. This composite coating system provides erosion resistance comparable to titanium while maintaining the lightweight aluminum substrate, resolving the contradiction between erosion resistance and weight.

The hard chrome coating is applied with varying thickness across different surfaces of the compressor wheel, with greater thickness at leading edges and lesser thickness at trailing edges. This local quality approach provides enhanced erosion resistance where needed most while minimizing additional weight and cost.

The bi-layered coating system combines electroless nickel-phosphorous base layer with hard chrome top layer to achieve erosion resistance at lower cost than titanium alloy. The electroless plating process is well-established and cost-effective, providing a economical solution that maintains reliability.

Instead of using expensive titanium alloy throughout the entire compressor wheel, the patent applies a relatively thin protective coating layer over a cheaper aluminum substrate. This approach provides the necessary erosion resistance at a fraction of the material cost of titanium.

The hard chrome coating thickness is varied across the compressor wheel surfaces, with greater thickness at leading edges where erosion is most severe and progressively lesser thickness toward trailing edges. This local quality approach maximizes erosion protection where needed while minimizing additional weight and rotational inertia.

Instead of applying uniform thick coating everywhere, the patent applies partial coating with optimized thickness distribution - sufficient thickness at critical erosion zones (leading edges) and reduced thickness at less critical areas (trailing edges), achieving adequate protection with minimal weight penalty.