Microstructure and Tribological Properties of AlCuFeSc Coatings: Effects of Surface Roughness and Quasi-Crystalline $i$-Phase Content

Abstract

High-velocity air-fuel (HVAF) spraying and detonation spraying (DS) methods are used to produce the Al-Cu-Fe-Sc coatings from a water-atomized powder on a low-carbon steel (Q235/SS330) substrate. X-ray diffraction phase analysis shows that the protective AlCuFeSc coatings produced by these methods contain different volume fractions of quasi-crystalline (QC) iphase. Wear and friction behaviour of the produced AlCuFeSc coatings is studied in the dry and wet conditions depending on the loading type (quasistatic or dynamic) for various counter-bodies (Si3N4, WC-Co hard alloy, or 52100 bearing steel). The effects of the coating-surface roughness and the QC i-phase content are also analysed.

Protection of AA2024 alloy against wear and corrosion by HVAF sprayed AlCuFe coating

“…High hardness magnitude H allows expecting the enhanced wear resistance that is consistent with the Archard-Rabinowicz equation suggesting the inverse proportionality of wear and hardness for materials with sufficient ductility [20,[28][29][30][31]. However, the low fracture toughness of quasicrystals (K 1C = 1.64 [46]) causes their low plasticity and thus brittleness at room temperature, which may facilitate excessive wear of abrasive mode.…”

“…Second, the coating comprises the relatively homogeneous mixture of two phases of different mechanical properties forming some kind of armoured material (Figure 3(e)): ψ-phase possesses a higher hardness while the β-phase is characterized by slightly lower hardness and better plasticity (indicated by arrows). This feature seems to promote load partitioning and timely relaxation in the coating surface layer tested, which results in better wear/friction behaviour [25][26][27][28][29][30][31]47,48]. Additionally, the porosity of the coating surface (Figure 3(d,e)), which facilitates better lubrication by the liquid paraffin, also promotes better wear resistance and lower CoF.…”

“…Thus, a magnetron sputtering [16], electron beam (EB) PVD technique [17,18], or plasma spraying [19][20][21][22][23][24] were used to produce the QC coatings. It was shown that their hardness and wear resistance values are comparable to or even higher than that of the natural composites containing QC particles distributed in the bcc β-phase [25][26][27][28][29], multi-phase alloys, or artificial Al-based composite layers containing QC particles [30][31][32]. The corrosion resistance of the QC coatings was shown to be high and comparable with that of stainless steel [33][34][35].…”