PROCESS FOR FORMING ULTRAFINE CRYSTAL LAYER, MACHINE COMPONENT HAVING ULTRAFINE CRYSTAL LAYER FORMED BY THE ULTRAFINE CRYSTAL LAYER FORMING PROCESS, PROCESS FOR PRODUCING THE MACHINE COMPONENT, PROCESS FOR FORMING NANO-CRYSTAL LAYER, MACHINE COMPONENT HAVING NANO-CRYSTAL LAYER FORMED BY NANO-CRYSTAL LAYER FORMING PROCESS, AND PROCESS OF PRODUCING THE MACHINECOMPONENT

摘要

A process for stably forming an ultrafine crystal layer on the surface of a metal product at a low cost. A hole part (1) is bored in a workpiece (W) by means of a drill (D) and a large strain is imparted to the inner circumferential surface of the hole part (1), thus forming an ultrafine crystal layer (C1). The inner circumferential surface of the hole part (1) is subjected to plastic forming with a true strain of at least 1, and the material temperature at the formed surface of the hole part (1) is maintained in a temperature range from the Ac1 transformation point to below the melting point. Alternatively, it is maintained at a temperature not exceeding the Ac1 transformation point. In such a way, an ultrafine crystal layer (C1) can be stably formed on the inner surface of the hole part (1) at a low cost.