| 摘要 |
Provided is a surface treatment method for safely, simply and quickly improving a powdered metal material to be used as a material in powder metallurgy, thermal spraying, or the like. The present invention involves: using a blast-machining device equipped with a dust collection means for spraying a spray powder and compressed air inside a work space and causing the same to collide with a collidable object, and removing and recovering dust by aspirating the interior of the work space; performing a blast treatment for repeatedly causing collisions at a spraying speed of 100-300 m/sec between a powdered metal material having an average particle diameter of 10-200[mu]m, and a medium material having a hardness equal to or greater than that of the powdered metal material; and detaching a surface oxide from the powdered metal material, and forming a fine-grain region which is near the surface of the powdered metal material and has a finer grain size than that of the center section thereof. The sintered metal obtained by sintering the powdered metal material subjected to the surface treatment has a concordant composition in which the fine-grain region and the large-grain region are concordantly arranged, and exhibits a balance of high ductility and high strength. |
