Laser chemical etching of metals in sodium nitrate solution

Abstract

A focused cw argon-ion laser has been used to etch several metals, including copper, molybdenum, nickel, niobium, and stainless steel in a 0.5M sodium nitrate neutral salt solution. Exceedingly smooth etch surfaces have been obtained for several of these metals with etch rates as high as 4 μm/s. Experiments were carried out as a function of laser intensity and laser dwell time to etch arrays of small holes, 100 μm or less in diameter on the different samples. From experiments performed in water under similar laser conditions we conclude that melt or near-melt temperatures are required to obtain etching in the salt solution. A comparison of the power required to produce incipient etching is made with calculated temperatures obtained for similar powers using a theory which approximates the experimental conditions. These calculated temperatures are reasonably close to the melt temperatures for most cases and offer supporting evidence for our etching model.