Quasicrystalline materials, especially Al–Cu–Fe systems, have attracted considerable attention due to their unique physical and chemical properties, such as high hardness, low friction coefficient, and good corrosion resistance. Plasma spraying is an effective method for producing quasicrystalline coatings, but post-processing is often required to improve their microstructure and tribological properties. This paper investigates the effect of laser processing on the microstructure and tribological properties of quasicrystalline Al–Cu–Fe coatings obtained by plasma spraying.
Al–Cu–Fe coatings were deposited on a steel substrate using plasma spraying. The resulting samples were laser processed with different parameters, including laser power and scanning speed. The microstructure of the coatings was studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Tribological properties were assessed by measuring the coefficient of friction and wear under dry friction conditions.
This paper presents the results of studying the effect of laser processing with flame hardening on the structure and tribological characteristics of coatings created by plasma spraying from a quasicrystalline Al–Cu–Fe alloy. Laser post-processing allowed us to obtain dense and durable coatings. It was found that the content of the icosahedral (i) phase is directly related to the laser power and scanning parameters.
It was found that the i-phase is formed at small values of the parameter δ (the ratio of the laser power P to the scanning speed v) due to the high cooling rate. A relationship was also found between the microhardness and the parameter δ. Due to the modification of the microstructure, laser post-processing significantly improved the tribological characteristics of plasma-sprayed QC Al–Cu–Fe coatings.
It was found that the friction behavior is determined by the phase composition of the coatings after laser processing. At the initial stage of testing, low friction coefficient values were observed for coatings with a high content of the i-phase. However, due to the brittleness of the i-phase, the differences in friction behavior decreased after 150 cycles, and the friction coefficient for all coatings that underwent laser post-processing stabilized at a level approximately two times lower than that of the plasma-sprayed coatings. A significant decrease in the wear rate after laser post-processing was observed only for coatings with a high content of the i-phase.
The results of the studies showed that laser treatment has a significant effect on the microstructure and tribological properties of quasi-crystalline Al-Cu-Fe coatings. Laser treatment leads to a decrease in porosity and an increase in the density of the coatings. In addition, a change in the phase composition is observed, leading to the formation of a more stable quasi-crystalline phase. Tribological tests showed that laser treatment leads to a decrease in the friction coefficient and an increase in the wear resistance of the coatings.
Laser post-processing is an effective method for improving the microstructure and tribological properties of quasi-crystalline Al–Cu–Fe coatings obtained by plasma spraying. Optimization of laser processing parameters allows obtaining coatings with high density, stable phase and improved tribological characteristics.
Author: W.DYuan, TM Shao, E Fleury, D Se, DR Chen
Institute: State Key Laboratory of Tribology, Building 9003, Tsinghua University, Beijing 100084, P.R. China, Center for Non-Crystalline Materials, Yonsei University, Seoul, South Korea