Impeller for rotary machine, compressor, supercharger, and method for producing impeller for rotary machine

An impeller for a rotary machine, comprising:

• a base material of the impeller comprising Al or an Al alloy;
• a surface layer for the impeller formed by an electroless plating layer comprising a Ni—P based alloy;
• and
• an under layer disposed between the base material and the surface layer, the under layer having a smaller Vickers hardness than the surface layer,
• wherein the surface layer has a P content rate of not less than 4 wt % and not more than 10 wt %.

An impeller for a rotary machine, comprising:

• a base material of the impeller comprising Al or an Al alloy;
• a surface layer for the impeller formed by an electroless plating layer comprising a Ni—P based alloy;
• and
• an under layer disposed between the base material and the surface layer, the under layer having a smaller Vickers hardness than the surface layer,
• wherein the under layer comprises a plating layer containing Ni.

An impeller for a rotary machine, comprising:

• a base material of the impeller comprising Al or an Al alloy;
• a surface layer for the impeller formed by an electroless plating layer comprising a Ni—P based alloy;
• and
• an under layer disposed between the base material and the surface layer, the under layer having a smaller Vickers hardness than the surface layer,
• wherein the under layer has a linear expansion coefficient between those of the base material and the surface layer.

A method of producing an impeller for a rotary machine, the method comprising:

• a step of forming an under layer on a base material of the impeller comprising Al or an Al alloy so as to cover the base material;
• and
• a step of forming an electroless plating layer on the under layer as a surface layer of the impeller,
• wherein the under layer has a smaller Vickers hardness than the surface layer, and
• wherein the surface layer is an electroless plating layer comprising a Ni—P based alloy having an amorphous structure, the Ni—P based alloy having a P content rate of not less than 4 wt % and not more than 10 wt % in the surface layer.