Tailored internal coating of components by PLD and pulsed laser evaporation

Abstract

An advanced PLD technique combining laser ablation and laser induced thermal evaporation was introduced to deposit thin films onto the inner surfaces of components. Beside the well known film properties of the classical PLD, like high reproducibility, smooth surface and high thickness precision, this novel combination of laser ablation and evaporation is characterized by improved or extended properties in terms of microstructure, deposition rate and possible layer thickness. The extension of the conventional PLD process allows for the co-deposition of dense, amorphous films as well as columnar grown or even porous films with thick nesses up to several tens of micrometers. In a first successful application of the novel process, tailored thermal barrier coatings (TBC s) for combustion chambers were realized. A remarkable result was that these coatings sustained very large strains of about 5% without notable delaminations. Under hot gas testing in model combustion chambers, the PLD-TBC s showed very promising behavior with excellent adhesion. Super hard, amorphous carbon films (DLC) deposited onto the inner surfaces of small components by this PLD technique are characterized by a Young s modulus of about 400500 GPa and a low friction coefficient of about 0.1. Due to its layered structure, with graded material density and hardness, this DLC exhibits relatively low internal compressive stresses of about -1...-2 GPa

Thin Film Deposition Using Energetic Ions

“…Nevertheless, it is still restricted as the origin of the deposited material is a small and isolated area, while the production of functional coatings on large and complex shaped substrates is associated with sophisticated manipulation systems. However, the formation of coatings on inner walls in restricted geometries is possible [ 71 ]. Considerable effort was invested in reducing the available laser pulse length in PLD towards the femtosecond regime while maintaining the pulse energy.…”