Analysis of Geometrical Characteristics and Properties of Laser Cladding 85 wt.% Ti + 15 wt.% TiBCN Powder on 7075 Aluminum Alloy Substrate

2020

Coatings with excellent mechanical properties are difficult to prepare on the aluminum alloy surfaces by laser surface engineering because of the low melting point and active chemical properties of aluminum (Al). Based on the unique entropy effect of a high-entropy alloy, we suppress the cracks in the cladding layer caused by the dilution ratio of the substrate, obtaining coatings exhibiting excellent wear resistance. The Al 0.8 CrFeCoNiCu 0.5 B x coating exhibited a BCC1+BCC2+FCC phase when the x0.1. When x0.2, boride was formed in the Al 0.8 CrFeCoNiCu 0.5 B x coatings, and it became the main phase of the Al 0.8 CrFeCoNiCu 0.5 B 0.3 and Al 0.8 CrFeCoNiCuB 0.4 coatings; however, no Alrich intermetallic compound with a complex phase structure was formed. When 0x0.3, the bonding strengths of the Al 0.8 CrFeCoNiCu 0.5 B x coatings were 70.6-176.2 MPa. An increase in the boron content increased the hardness of all the coatings, except the Al 0.8 CrFeCoNiCu 0.5 B 0.3 coating.The hardness was 479-705 HV (6-9 times that of the substrate). The wear rate of the coating ranged from 1.50×10 −7 to 1.19×10 −5 mm 3 /Nm, which was only 0.01%-5.43% that of the substrate. The Al 0.8 CrFeCoNiCu 0.5 B 0.2 coating exhibited the highest resistance to wearing, and its wear mechanism was identified as abrasive wear.

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Microstructure and wear resistance of the laser-cladded Al_0.8CrFeCoNiCu_0.5B_x high-entropy alloy coating on aluminum

2020

“…From the classical electrochemical theory, the free corrosion potential (E corr ) only represents the thermodynamic trend of the WE during the corrosion process, while the free corrosion density (I corr ) is caused by the dissolution of the WE. I corr is determined in the linear part of the polarization curve by deducting Tafel extrapolation, where the polarization resistance (R p ) is calculated according to formula (6). Therefore, I corr is the most important index for evaluating the corrosion resistance of WE [34][35][36].…”

Section: Wear Testmentioning

confidence: 99%

“…However, due to poor surface hardness and low wear resistance, its application has been limited in some top-end areas. In recent years, surface treatment, such as electroplating, physical vapor deposition (PVD) and laser cladding (LC) [4][5][6], have been gradually applied for the surface modification of aluminum alloy. Among them, LC has stood out due to its features of less pollution, high efficiency, and the preparation of thicker coatings.…”

Section: Introductionmentioning

confidence: 99%

Microstructure, mechanical, and corrosion resistance properties of Al_0.8CrFeCoNiCu_x high-entropy alloy coatings on aluminum by laser cladding

Olugbade

2020

High-entropy alloys (HEAs) were used to improve the hardness, wear resistance, and corrosion resistance of steel surfaces by laser cladding due to their outstanding mechanical and corrosion resistance properties. However, there are only a few literary works on the improvement of wear resistance on the aluminum alloy surface by HEAs. In this work, the wear performance of laser cladded Al 0.8 CrFeNiCoAlCu x HEA coating on aluminum alloy with different Cu contents was investigated in detail. Moreover, phase structure, microstructure, bonding shear strength, and corrosion resistance of HEA coatings were studied by XRD, SEM, tensile device, and electrochemical workstation. The result shows that with the increase of the Cu content, the structure of the coatings changed from BCC1 and BCC2 phases to BCC1, BCC2, and FCC1 phases. Evident cracks were observed in the Al 0.8 CrFeCoNi HEA coating. Meanwhile, when x=0.25, the cracks disappeared, but the bonding shear strength was 79.6 MPa, only 34.7% of the substrate. At 0.5x1, the bonding shear strength of the Al 0.8 CrFeCoNiCu x HEA coatings went above 175.2 MPa. As Cu promotes the formation of FCC phase, the hardness of the Al 0.8 CrFeCoNiCu x HEA coating decreased as the Cu content increased. The effect of Cu on wear resistance has the same trend as with hardness. The wear rate of Al 0.8 CrFeCoNiCu 0.5 , Al 0.8 CrFeCoNiCu 0.75 , and Al 0.8 CrFeCoNiCu HEA alloys is only 3.4%, 4.02%, and 5.42%, respectively, of the substrate. The wear mechanisms of the substrate are that of delamination fracture and serious adhesion wear, while the wear mechanisms of Al 0.8 CrFeCoNiCu x (0.5x1) HEA coatings are that of adhesive and abrasive wear. The corrosion resistance of Al 0.8 CrFeCoNiCu x (0.5x1) HEA is better than that of the substrate in 1 mol l −1 H 2 SO 4 solution. Al 0.8 CrFeCoNiCu 0.5 has the best corrosion resistance that is characterized by pitting and intergranular corrosion.OPEN ACCESS RECEIVED increase the cracking sensitivity and affect the performance of the coating [7-10]. Therefore, the preparation of coatings on aluminum alloy has always been a problem in the field of LC.High-entropy alloy (HEA) has persistently been a hot research subject in the field of materials science [11][12][13], since it was developed in 2004. HEA is generally defined as alloys formed by five or more elements with a molar ratio between 5% and 35% and having an entropy greater than 11. RJ mol −1 ·K −1 [14]. HEAs have high strength and hardness, good corrosion resistance, and excellent thermal stability [15]. Khan et al [16] prepared a film of AlCrFeCoNiCu 0.5 HEA using magnetron sputtering technology and found that the alloy had an FCC and BCC dual-phase structure and a hardness value of 13 GPa. Luo et al [17] prepared the WC+Al x CrFeCoNiCu (0x1.5) composite by mixing WC with Al, Cr, Fe, Co, Ni, and Cu powders, by plasma sintering. Due to slow diffusion effect, the WC particles dispersed in the solid solution phase of HEA, and the WC+Al 0.5 CrFeCoNiCu composite exhibited a ...

“…However, due to the lower hardness and poor wear-resistance of aluminum alloy surfaces, its applications are limited in cutting-edge areas where reliability is more demanding. The popular aluminum alloy surface strengthening methods include chemical plating, electrodeposition techniques, and laser cladding(LC) [5][6][7][8]. Compared with other coating technologies, the laser cladding method has the advantages of producing lower pollution, higher efficiency, and thicker coating and a smaller heat-affected zone [9].…”

Section: Introductionmentioning

confidence: 99%

Phase assemblage and properties of laser cladded Ti_xCrFeCoNiCu high-entropy alloy coating on aluminum

2020

The Ti x CrFeCoNiCu(x:molar ratio, = x 0, 0.2, 0.5, 0.8, or 1.0) coating was depositd on aluminum by laser cladding. The phase structure, microstructure, hardness, wear resistance and corrosion resistance were studied. The results show that with the increase of Ti content, the phase structure of the Ti x CrFeCoNiCu coating changes from single FCC to FCC+B2, and FCC+Laves phase. When Ti is increased to 1.0, cracks appear in the coating. The hardness of the Ti x CrFeCoNiCu coating is enhanced with the increase of Ti content, and ranges from 215HV 0.2 to 585HV 0.2 , which is about 3 to 7 times that of the substrate. The strengthening mechanism of Ti 0.2 CrFeCoNiCu is solid solution strengthening, and when the Ti content is greater than 2, the strengthening mechanism of Ti x CrFeCoNiCu coating is precipitation strengthening. The influence of Ti on the wear resistance exhibits the same trend as with hardness. When Ti increased from 0 to 0.8, the wear rate of the Ti x CrFeCoNiCu coating changed from´--2.26 10 mm Nm 4 3 1 to´--9.92 10 mm Nm : 7 3 1 smaller than the substrate. The addition of Ti increases the current corrosion density of Ti x CrFeCoNiCu coating, but both coatings still exhibits superior corrosion resistance relative to the substrate.