Patent ID: 9096913
Filing Date: 2015-08-04
Classification: C21D

Abstract:
1. A process for creating internal stress in a metallic workpiece by laser shock peening, comprising the steps of: forming a slightly ionized pre-plasma by applying a first laser pulse, having a first energetic condition, to a treatment site of the workpiece covered by a surface layer to evaporate a portion of the surface layer and form the slightly ionized pre-plasma, forming a quasi-static plasma from the slightly ionized pre-plasma by applying a second laser pulse, having a second energetic condition, wherein the second laser pulse has an energy level that is higher than an energy level of the first laser pulse, and the second laser pulse is applied to the treatment site of the workpiece at an interval of from 5 nsecs to 100 nsecs after the first laser pulse, and providing a covering layer over the treatment site during the application of the laser pulses, wherein the first energetic condition is one that forms the slightly ionized pre-plasma without forming the quasi-static plasma, wherein the first energetic condition is insufficient to form plasma and cause expansion of an unsteady plasma, and wherein the second energetic condition is one that forms the quasi-static plasma from the slightly ionized pre-plasma.