| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface treatment method which modifies a powder metal material to be used in e.g. powder metallurgy and flame spray, safely and simply in a short time.SOLUTION: A surface treatment method uses a blast processing apparatus which injects an injection powder, together with a compression gas, within a workspace to cause the powder to impinge on a to-be-collided object and is provided with dust collection means of sucking powder dust from the workspace to remove and recover the powder dust. The surface treatment method comprises: carrying out a blast treatment by causing a powder metal material of an average particle size of 10-200 μm and a medium material having a hardness comparable with or higher than the hardness of the powder metal material to collide repeatedly with each other at an injection speed of 100-300 m/s, so as to peel a surface oxide from the powder metal material; and forming fine particle regions having crystal grain sizes smaller than crystal grain sizes in the central part, in the vicinity of the surface of the powder metal material. A sintered metal obtained by the powder metal material subjected to the surface treatment has a harmonious structure in which fine particle regions and coarse grain regions are arranged in a harmonized way and achieves high ductility and high strength at the same time. |
