Entropy Alloy Coatings Research Articles

Optimized wear behaviors and related wear mechanisms of medium entropy alloy-based composite coatings

In this work, the (10 wt%, 30 wt%, 50 wt%) TiC reinforced AlFeCrCo medium entropy alloy (MEA) lightweight composite coatings with the extremely low porosity were successfully fabricated on Mg alloy substrate by resistance seam processing. The results showed that the microstructure of composite coating was consisting of a BCC-based MEA matrix and TiC particles, and a good metallurgical bonding with a semi-coherent relationship was formed between the coating and Mg alloy. Furthermore, the lightweight composite coatings (5.6–6.5 g cm−3) showed improved corrosion resistance over Mg alloy substrate. Specifically, the composite coatings exhibited optimized wear performance in the dry, deionized water and 3.5 wt% NaCl solution conditions with the increasing TiC content, surpassing related high/medium entropy alloy coatings, which is attributed to the formation of a coherent interface between the MEA matrix and the TiC particles. The first-principles calculations were performed to elucidate the nature for the higher bonding strength of TiC/MEA interface. In these wear conditions, the main wear mechanisms of composite coatings were discussed in terms of adhesive wear, oxidative wear and/or corrosive wear, in connection with their microstructure features and electrochemical behaviors. Based on the elevated anti-corrosion ability, this work has provided a strategy to fabricate advanced coatings on Mg alloys endowing with lower density, interfacial metallurgical bonding and optimized wear resistance, substantially contributing to the development of high-performance composite coatings.

Enhanced Corrosion−Resistance of AlTiCrFeMoSi High−Entropy Alloy Coating by Magnetron Sputtering

The amorphous AlTiCrFeMoSi high entropy alloy (HEA) coating with high hardness (11.88 GPa) is successfully deposited on T91 substrate by the magnetron sputtering method. Both T91 steel and as−deposited AlTiCrFeMoSi coating samples are exposed to a static liquid lead−bismuth eutectic (LBE) at 550 °C for up to 2000 h. The coating exhibits excellent corrosion resistance against lead−bismuth eutectic (LBE) compared with the uncoated T91 steel. The results show that the AlTiCrFeMoSi HEA coating has great potential in LBE−cooled fast reactor application.

Effect of annealing temperature on the thermal stability of FeCrNiMnMoxSi0.5B0.5 coatings

ABSTRACTIn order to acquire high entropy alloy (HEA) coatings with outstanding thermal stability, FeCrNiMnMoxSi0.5B0.5(x = 0, 0.8, 1.0) HEA coatings were prepared on Q235 steel by the laser cladding technique. The phase structure, microstructure and microhardness of the HEAs were carefully investigated by a scanning electron microscope (SEM), X-ray diffraction (XRD) method and a microhardness tester, respectively. The experimental results show that FeCrNiMnMoxSi0.5B0.5(x = 0, 0.8, 1.0) HEAs consist mainly of face-centred-cubic (FCC) solid solution plus a few FeMoSi phases, the microstructure evolves from wheat-shaped dendrite to net-like dendrite with the addition of Mo element. The microhardness of as-cladded coatings increases with the addition of Mo content, especially the FeCrNiMnMo1Si0.5B0.5 coating. However, the microhardness change of annealed coatings is closely related to the number of intermetallic compounds and lattice distortion intensity of FCC solid solution.

Effect of Mn Contents on the Phase Transition of the High Entropy Alloy Prepared by Laser Cladding

Al1.3FeCoNiCuCr high entropy alloy (HEA) coatings were prepared by pre-placed laser cladding on 921A steel substrate, and the study on the phase transition of the Al1.3FeCoNiCuCr coating due to the introduction of Mn was conducted. The combination of TEM and XRD results showed that the Al1.3FeCoNiCuCr HEA coatings without Mn addition typically consisted of two kinds of grains, i.e., one is composed of only FCC phase, and the another is a mixture of BCC and FCC phases. The two phases were of similar ratio in the coatings, while nanoparticulate precipitates were observed in the bcc phase. When 3 wt. % Mn was introduced into the alloy, the coatings consisted of also FCC and BCC phase. However, most of the grains were in FCC phase, while the BCC phase with a lath shape only distributed between the FCC phases. High hardness nanobanded precipitates were observed in the FCC phase. It is clearly revealed that the phase structure of Al1.3FeCoNiCuCr coatings undergoes a dramatic transition due to the introducing of Mn.

Two-step Laser Cladding of AlCoCrCuFeNi High-entropy Alloy on AZ91-Mg

AlCoCrCuFeNi high entropy alloy (HEA) coatings were formed on AZ91-Mg substrates using a two-step laser cladding technique that was adopted to solve the HEA melting problem due to the large difference in their melting temperatures. First, a layer composed of partially melted HEA powders in an AZ91 Mg matrix was produced, i.e. a composite layer, followed by laser cladding on the composite layer surface. The results showed that the top layer of the coating had a bcc solid solution structure and no intermetallic compound was detected. The dilution behaviour and the reactions between the HEA powder and the matrix were studied. In the composite layer, the Cu from the HEA powder was the main element that entered into the substrate melt, however, no serious dilution occurred. The solidification reactions at the HEA powder surface were determined using the corresponding Mg-Al-Cu phase diagrams that were constructed based on the CALPHAD approach.