Coated rotary tool and method for manufacturing the same

1. A friction stir welding tool used for friction stir welding, comprising:

a base material; and

a coating layer formed on a surface of at least a portion of said base material that is to be caused to contact workpieces during friction stir welding,

said coating layer containing cubic WC 1-x ,

said base material being formed of a cemented carbide, and

said cemented carbide having a thermal conductivity of not more than 43 W/m·K.

2. The friction stir welding tool according to claim 1 , wherein said base material contains WC having an average particle size of not less than 0.1 μm and not more than 1 μm.

3. The friction stir welding tool according to claim 1 , wherein said base material contains not less than 3% by mass and not more than 15% by mass of Co.

4. The friction stir welding tool according to claim 1 , wherein said coating layer is formed by a physical vapor deposition method.

5. The friction stir welding tool according to claim 1 , wherein said coating layer subjected to x-ray diffraction has I (WC 1-x )/I (W 2 C) of not less than 2, where I (WC 1-x ) is a higher one of respective diffracted beam intensities of (111) diffracted beam and (200) diffracted beam, and I (W 2 C) is a highest one of respective diffracted beam intensities of (1000) diffracted beam, (0002) diffracted beam, and (1001) diffracted beam.

6. The friction stir welding tool according to claim 1 , wherein friction stir welding by means of said friction stir welding tool is spot joining.

7. A method for manufacturing a friction stir welding tool including a base material and a coating layer, comprising the step of forming, by a physical vapor deposition method, said coating layer on a surface of at least a portion of said base material that is to be caused to contact workpieces,

said coating layer containing cubic WC 1-x ,

said base material being formed of a cemented carbide, and

said cemented carbide having a thermal conductivity of not more than 43 W/m·K.