High-velocity laser accelerated deposition (HVLAD): An experimental study

Abstract

A versatile solid-state cladding technique named high-velocity laser accelerated deposition (HVLAD), which is capable of creating highly uniform coverage on various surfaces, is reported here. The method is a non-thermally driven, mechanically based process that relies on laser peening (LP) technology which has been used for commercial applications for decades. In HVLAD, a high-intensity laser is used to accelerate, propel, and deposit small areas of a thin film in a controlled step-by-step manner onto a substrate. This process can be repeated until a desired thickness of material is deposited onto the substrate. This technique does not generate any large variations in temperature between the thin film and the substrate material. Instead, it employs intense laser pulses with energies up to 50 J for a duration of 8–50 ns to create a plasma generated pressure wave which accelerates the thin film in the order of a few hundred meters per second into the substrate material. Two cladding methods were evaluated in this study including the confined method, which incorporates a confining water media and a vinyl tape overlay, and the unconfined method which does not. High speed and thermal imaging cameras showed no macrolevel melting or significant temperature increase in the clad or substrate material during the cladding process, however signs of microlevel melting and re-solidification were observed at the interface primarily in specimens cladded using the unconfined method. Grain structures in adjacent areas to the clad location remained preserved using both methods, and no signs of any phase or alloy composition changes, except for at the interface, were observed. The effects of a confining media (water) and vinyl tape in the process were studied both analytically and experimentally and a change in the deposition mechanism was observed. With further research and development this technique has the ability to be used to deposit a variety of coatings without any limitations dictated by their strength on complex geometries in a cost-effective manner. The HVLAD process can be implemented to deposit corrosion, wear, thermal, and even impact-resistant coatings with strong bonding on a wide range of substrates.