Mon, 14 December, 2020
For the Geo-Coat project, University “Politehnica” of Bucharest, developed and deposited thin layers of high entropy alloys produced by solid state processing method.
"Our experience in the mechanical alloying field, represented an important advantage in this project. The materials produced by this method exhibit a high alloying and homogenization degree, but also no oxidation or contamination issues due glovebox manipulation", says Laura Geambazu, as she talks about the coatings works at University "Politehnica" Bucharest.
The mechanical alloying process was conducted by using a FRITSCH® Pulverisette 6 Classic Line Planetary Mill, equipped with stainless steel balls and vial and argon atmosphere. In order to facilitate alloying, n-heptane was used as process control agent. Wet milling with n-heptane is preferred due to the good results obtained from previous experiments. Wet milling prevents the powder mixture to weld to the vial walls and helps the powder particles to weld and be crushed again repetitively to ensure a homogeneous mechanical alloying process.
In order to reduce downtime through failures/and or treatments of the work equipment, coatings were produced by electro spark deposition technique (ESD). The advantage of this method, besides the low quantity of material that is consumed during the process, is represented by the possibility of local restoration or repairs of heavy duty in work equipment.
Coating different material substrates with high entropy alloys was a challenge due to the novelty of the process, but by testing and optimizing the parameters, we were able to obtain what we proposed.
For the ESD process, the coatings are obtained by using a miniature applicator. The parameters are selected in accordance with the type of materials that will be used. Being a manual process, the layer thickness and the surface topography can be optimized and due to the continuous flow of argon on the surface, the oxidation is reduced to a minimum value.
Article Courtesy: Laura Geambazu, University "Politehnica" Bucharest, MSEF.