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As aircraft and thermoelectric turbine blades work in aggressive environments (high temperatures and pressures), they are exposed to oxidation reactions. Ceramic coatings are employed to increase the turbine work temperature (improving its performance) and a bond coat (BC), base of particulate material of Ni-Cr-Al powders, which assure a good adhesion, gradual decrease in thermal expansion coefficient between the metallic substrate and the ceramic top coat, avoiding the oxidation effect in the metallic substrate. This research aims the study and comparison of two different deposition process routes of particulate materials of BC (MCrAlY) on AISI 316 stainless steel substrate. In the first case, the BC powder was pre-deposited by segregation method and irradiated by a CO2laser beam. In the second case, laser surface texturing was done on the stainless steel surface by a Yb: fiber laser beam, the BC was deposited by the same method, and further, irradiated by a CO2laser beam. The main focus of this work was to evaluate the resulting interface for both mentioned cases. For this propose, characterizations were made using the techniques of optical microscopy and roughness measurements. In the first case, homogenous layers of bond coat were obtained. Optical microscopy suggest the formation of a metallurgic bonding between the substrate and the MCrAlY. For the laser surface texturing, the surface roughness can be adjusted by the laser beam parameters.

This study investigate the laser surface hardening in tool steel, avoiding the high reflectivity of the metal to the CO2 radiation by covering the surface sample with black carbon. Hardening process using graphite was effective in many works in the word, although, the particles size of graphite powder was in the range of some micrometers. In order to reduce the particle size, the carbon black was used in the laser thermal treatment of 4340 steel. The microhardness change to 850HV, compared to the substrate of 250HV and the friction coefficient ranged 0.2 and 0.3, because of the covered surface by carbon black. These thin coating of carbon black reduced the wear rate near to a hundred in comparison to the surface without carbon coating.

Coatings are applied on turbine blades’ surfaces to provide protection not only against high temperature but also against aggressive environment. Ceramic coatings are employed to avoid metallic substrate overheating, while at the same time increasing turbine work temperature and performance. A bond coat (BC) base of particulate material based on Ni-Al powders is necessary to assure oxidation protection, a good adhesion and gradual decrease in thermal expansion coefficient between the blades’ metallic substrate and the ceramic top coating. One of the most important parameters of such coatings is the adhesion strength. In this work, a NiCrAlY bond coat was deposited on Inconel 625 substrate employing High-Velocity Oxygen-Fuel (HVOF) thermal spraying technology and CO2 laser beam irradiation to enhance coating–substrate adherence and metallurgical bonding. Microstructural features were examined by optical and scanning electron microscopy (SEM), X-ray diffraction and microhardness analysis. The results indicate that the laser treatment provided an efficient metallurgical bond between the (BC) and Inconel 625 substrate.

Ceramics are widely employed as thermal insulating materials for thermal barrier coatings (TBC) due to their low thermal conductivity, chemical stability, and high wear and corrosion resistance at high temperatures. The aim of this work was to study the influence of the CO 2 laser beam parameters on the single-step irradiation of pre-placed yttria-stabilized zirconia (YSZ) powders on NiCrAlY/AISI 316L substrates. In order to increase the coating's lifetime and performance, it is proposed a laser sintering of powder-beds (LSP) technique to obtain homogenous YSZ coatings, with controlled surface microstructures. The obtained coatings were characterized by optical microscopy, field emission scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction (XRD). The laser intensity and interaction time were the main laser parameters used to control the surface temperature and the combination of these parameters were used to establish a process chart. The LSP resulted in controlled smooth coating surfaces and columnar growth with submicrometric grain size. XRD analyses showed the prevalence of non-transformable tetragonal zirconia, which is known to exhibit higher stability and thermal wear resistance.