Corrosion Behavior of Laser Remelted CoNiCrAlY Based Composite Coatings

Abstract

The corrosion behavior of High-Velocity Oxygen Fuel (HVOF) sprayed MCrAlY coatings obtained from CoNiCrAlY particles (wt. 8% Al) mechanically doped with Al 2 O 3 nanopowder was investigated before and after laser remelting. The latter process was applied in order to achieve a homogeneous structure as well as better mechanical properties for the coating (reduced brittleness offered by the presence of the Al 2 O 3 nanoparticles). Another important task of the laboratory investigations was the investigation of the corrosion behavior of the modified coatings. The results obtained from the potentiodynamic polarization measurements carried out in a chloride environment revealed an enhanced corrosion resistance of the laser remelted coatings comprising a refined microstructure. Microhardness measurements of the modified coatings revealed lower values in comparison with that of the samples in as-sprayed status. This observation leads to the assumption that a concomitant improvement of coatings ductility occurred as well.

Preparation of MCrAlY–Al2O3 Composite Coatings with Enhanced Oxidation Resistance through a Novel Powder Manufacturing Process

“…Efforts have been made to develop MCrAlY-Al 2 O 3 composite coatings with dispersion of Al 2 O 3 particles on the surface as nucleation sites to promote the early formation of a coherent a-Al 2 O 3 scale (Ref [16][17][18][19][20]. The challenge is, however, there is no established process to prepare composite powder feedstock with a homogenous distribution of the second phase particles with submicron or nano-sizes that are prone to agglomeration (Ref 6).…”