激光诱导等离子体在材料表面强化中的应用

Applications of Plasma Induced by Laser Shock on Surface Treatment

激光冲击强化(Laser Shock Processing)又称激光喷丸(Laser Peening)是一种新型表面强化技术,是利用高功率密度(可达GW/cm2)、短脉冲(ns量级)激光辐照材料表面时,材料表面的表面吸收层(涂覆层)吸收激光能量发生爆炸性汽化蒸发,产生高压(GPa)等离子体,该等离子体受到约束层的约束爆炸时产生高压冲击波,作用于金属表面并向内部传播。在材料表层形成密集、稳定的位错结构的同时,使材料表层产生应变硬化,残留很大的压应力,显著的提高材料的抗疲劳和抗应力腐蚀等性能。介绍了激光诱导等离子体的原理、激光在材料表面诱导冲击压力模型、激光冲击致材料表层纳米化、激光冲击诱导等离子体强化技术应用于钛合金和铝合金在航空工业中的应用,并对该技术的国内外研究现状进行了阐述及展望。

Laser shock processing, also called laser peening, is a novel advanced surface treatment technology. The laser pulse with high peak value power （〉1 GW/cm2 ）, short duration （nano second level） irradiates on the surface of coating layer traveling transparent confining layer by focusing lens. The coating layer absorbs the laser energy, explodes and forms plasma in very short time. The plasma is restrained by the confined medium during expanding and products high pressure shock wave. When the peak value of stress wave exceeds the HEL （Hugoniot Elastic Limit） of the target for a suitable time, the dense and stable dislocations are formed. The surface strain hardening is produced at the same time. The microstructure alteration and the existence of compressive residual stress improve the fatigue performance of material surface. The principle of LSP was introduced as well as pressure model of laser shock, nanocrysrallation induced by laser shock and the applications on aeronautical industry of LSP titanium and aluminum alloys.