High-temperature wear behaviour of ZrC/NbC-reinforced CrMnFeCoNi coatings

Nowadays, studies of high entropy alloys (HEAs) have shown excellent properties. To improve the high-temperature wear resistance of CrMnFeCoNi alloy, refractory carbides (NbC and ZrC, respectively) reinforced CrMnFeCoNi composite coating were prepared by laser cladding (LC), and its wear performance was investigated. The composite coating showed no cracks or other defects that had metallurgical bonding with the substrate. Those coatings exhibited oxidative and adhesive wear mechanisms in reciprocating wear tests at 600°C. In contrast to the strengthening of NbC, the ZrC in the coating rapidly oxidized during high-temperature wear, forming a large amount of ZrO2. These oxides formed in wear promote the formation of a protective film, further improving the oxidation resistance and wear resistance of the coating

Effect of Heat Dissipation Rate on Microstructure and Mechanical Properties of Al0.5FeCoCrNi High-Entropy Alloy Wall Fabricated by Laser Melting Deposition

High-entropy alloys (HEAs) are a new type of multi-component alloy. The design of the compositions breaks the design ideas of traditional alloys and shows many excellent properties. Therefore, an Al0.5FeCoCrNi HEA with face-centered cubic (FCC) and body-centered cubic (BCC) dual-phase structure was used in this paper. During the additive manufacturing process, the heat dissipation rate gradually changes with the increase in wall height. As a result, the composition of the phases changes, resulting in differences in mechanical properties. Here, we designed laser melting deposition (LMD) on T-beams of different heights to change the heat dissipation rate of the wall, and the effects of the heat dissipation rate on the microstructure and mechanical properties of Al0.5FeCoCrNi HEAs were studied. The experimental results showed that increasing the height of the T-beam would gradually slow down the heat dissipation rate of the wall. The above phenomena not only led to a gradual reduction of the BCC phase under the influence of heat accumulation but also increased the length of columnar crystals in the wall with the slowing of heat dissipation. Heat accumulation hindered the nucleation during solidification and eventually led to the growth of grains across the deposition layer. Furthermore, the slow heat dissipation rate changed the grain number and BCC phase content, which gradually decreased the strength and hardness, while the ductility of the samples improved

Effect of High-Temperature Heat Treatment on Strengthening Mechanism of AlCoCrFeNi Component Fabricated by LMD

In the present study; an AlCoCrFeNi high-entropy alloy (HEA) component was produced by laser melting deposition (LMD) technique. Then; a heat-treatment process based on the detection results of Differential Scanning Calorimeter (DSC) was used. The effects of heat treatment on the phase transition; microstructure and mechanical properties of the AlCoCrFeNi component were systematically studied. The results showed that low-temperature heat treatment (600 °C) had little effect on the microstructure and mechanical properties of component. The 800 °C heat treatment precipitated σ and face-center cubic (FCC) phases near grain boundaries in the component. The high dislocation capacity of FCC phase and precipitation strengthening of σ phase improved the strength and plasticity of this component. However; hard and brittle σ phase was not conducive to uniform distribution of microhardness. High-temperature heat treatment (1000 °C) caused the σ phase to remelt and increased FCC phase content at grain boundaries; resulting in a significant increase in strength and plasticity. Although the microhardness of the AlCoCrFeNi component after this heat treatment was reduced; the good strength and plasticity will facilitate its application in the structural field

The Wear Properties of TiC/Al-Based Composite Coating Applied by Laser Cladding

Aluminum powders with different concentrations of TiC ceramic particles were applied to an AZ31B magnesium alloy by laser cladding. Due to differences in coefficients of thermal expansion, the distribution of TiC ceramic particles in the cladding layer was not uniform. The results show that the degree of TiC ceramic particle agglomeration in the cladding layer increases with increasing TiC content. The phases of cladding metal mainly consisted of Al, γ-Al12Mg17, β-Al3Mg2, and TiC. The γ-Al12Mg17 phase mainly distributed to the bottom of the cladding layer, and the β-Al3Mg2 phase distributed to the middle and surface areas. The existence of the γ-Al12Mg17 phase enhanced the hardness of the fusion zone. The microhardness of the cladding layer increased with increasing TiC ceramic particle content. An appropriate TiC content improved the wear resistance of the cladding layer. When the TiC content was excessive, the agglomeration behavior of TiC ceramic particles strongly affected the wear resistance of the coatings

A novel gradient composite material CrMnFeCoNiB2C0.5 prepared by laser melting deposition

A novel gradient composite of CrMnFeCoNiB2C0.5 was prepared by laser melting deposition (LMD). The heat accumulation during LMD results in thin-walled structure that exhibit significant structural gradients. The material was tested with an ultimate compressive stress of 1.56 ± 0.067 GPa and a compressive strain of 19.17 ± 1.96%. Such materials have the potential to prepare additive manufactured parts with locally-controllable strength and plasticity by simply varying the thermal input only

Effects of Laser Powers on Microstructures and Mechanical Properties of Al0.5FeCoCrNi High-Entropy Alloys Fabricated by Laser Melting Deposition

High-entropy alloys (HEAs) show great promise for various applications in many fields. However, it still remains a challenge to obtain the ideal match of the tensile strength and the ductility. In this paper, Al0.5FeCoCrNi walls were fabricated through laser melting deposition (LMD) technology with laser power ranging from 1000 W to 1800 W. Along with the increase in laser power, the average size of the Al0.5FeCoCrNi walls increased from 14.31 μm to 34.88 μm, and the B2 phase decreased from 16.5% to 2.1%. Notably, the ultimate tensile strength and the ductility of the 1000 W bottom wall were 737 MPa and 24.6%, respectively, while those of 1800 W top wall were 641 MPa and 27.6%, respectively, demonstrating that the tensile strength of the walls decreased and the ductility increased with the increase in laser power. Furthermore, quantitative calculation revealed that grain boundary strengthening and dislocation strengthening were the two major forms of strengthening compared to the others. This study concluded that the mechanical properties of HEAs could be regulated by laser power, enabling broader applications in industry with favorable tensile strength or ductility