PURPOSE: To eliminate unnecessary stress to remain plied to a blade and prevent deformation of the blades in fixing an anticorrosion piece on a front edge of the blades.

CONSTITUTION: An anticorrosion piece 3a is composed of three layers. A first layer is an alloy steel including 25.0wt% of Co, 12.0wt% of Cr, 2.5wt% of C, and balance of Fe. A second layer is an alloy steel including 35.0wt% of Co, 12.0wt% of Cr, 2.5wt% of C, and balance of Fe. A third layer is an alloy steel including 45.0wt% of Co, 25.0 to 30.0wt% of Cr, 2.5wt% of C, 15.0 to 20.0wt% of W, and balance of Fe. These three layers are deposited.