David Merino-Millan

Nickel-based coatings provide outstanding wear and erosion resistance making them particularly suitable for several applications, from aerospace and naval to automotive, energy, and electrical. Cold spray (CS) is encountering a growing interest as a promising technology to deposit thick and dense coatings for components used in energy power generation systems, such as the concentrating solar power (CSP) plants. In this article, nickel coating was deposited onto steel substrates by using a low-pressure CS. The erosion behaviour of the coating was evaluated by a solid particle impact test at two different impact angles. The coating erosion rate was 10 × 10⁻⁴ at a 60° impact angle, showing a combination of ploughing and cutting mechanisms.

The current developments in concentrating solar power are focused in the third generation. Increase the working temperature of the plants is the main objective for this new generation. For this new condition, alternative materials for the receivers must be explored. In this work, a nickel alloy coating has been fabricated using a compact plasma spray system to be used on the receiver. This thermal spray system could be used for in-situ maintenance and overhaul as it is portable. Then the coatings have been exposed at high temperature of 800 ºC, as expected in the third generation, during different exposure times. The evolution of the coating solar absorptivity and adherence have been studied over the selected exposure times. A maximum value of solar absorptivity 0.93 was reported for the longer exposure time studied. The adherence increment was remarkable reaching a value of about 57 MPa. These results show that these coatings could represent a durable alternative while the solar absorptivity maintains high values.

Nickel-based coatings are widely used as thermal barriers in several sectors thanks to their remarkable corrosion and wear resistance and outstanding stability at high temperatures. Recently, Ni coatings, produced with thermal spraying and vacuum techniques, have been investigated for solar power energy applications. In the present manuscript, low-pressure cold spray (LPCS) was used to deposit pure Nickel onto a steel substrate. The influence of gas temperature, nozzle stand-off distance, and advancing speed on morphological and mechanical properties were studied. The optimal deposition conditions were derived by ANOVA analysis. The hardness and the adhesion strength were approximately 160 HV and 26 MPa, respectively. The highest thickness obtained under the optimised deposition with a single pass was around 900 µm.