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The present study reports on nucleate boiling tests performed with specifically textured chromium nitride (CrN) coatings exhibiting either predominant (1 1 1), (2 0 0) or (2 2 0) crystal lattice orientations. Those tests reveal promising results concerning thin film applications in the field of heat transfer enhancement during nucleate boiling. High power impulse magnetron sputtering (HiPIMS) in combination with direct current magnetron sputtering (DCMS) was applied to deposit CrN coatings of 4.5 μm thickness on average. A thin coating of pure chromium (Cr) was used as adhesive interlayer between substrate and CrN coating. The crystallographic phases and orientations of the coatings were determined by X-ray diffraction (XRD) in θ/2θ mode and texture coefficients T c (h k l) were calculated. High resolution scanning electron microscope (SEM) visualizes the shapes, sizes and orientations of the grains. Different Cr|CrN coating systems were deposited on pure copper heater samples and boiling curves were measured in nucleate boiling experiments in order to determine heat transfer coefficients (HTC) and critical heat flux (CHF) at dry out of the heater surface. Final comparison among the coatings' heat transfer properties reveals differences in CHF and HTC of a factor of 1.8, respectively 1.6, according to the applied microstructure.

Imperfection on substrate surfaces commonly causes growth defects in hard coatings prepared by magnetron sputtering, leading to local loss of adhesion, higher friction, voids and corrosion at coating defects. CrN coatings are known for their high hardness and good wear resistance. The structure and the mechanical properties of those coatings can be influenced varying bias voltage and gas flow during film growth. Due to variation of those parameters CrN coatings were deposited with preferred crystallized lattice orientations (111) and (200). The main objective of investigation is the potential to cover imperfections to increase robustness, especially under superimposed corrosive loads. With the intent to generate comparable surface defects, Vickers indentations were applied as artificial imperfections. With X-ray diffraction analysis and cross-sectional SEM micrographs film orientation and texture around those artificial imperfections was studied, aiming to examine coating microstructure and grain growths. In this context the potential of specified crystallized lattice orientation to cover imperfections is of particular interest.