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In this paper, a Cu–Mo alloying layer with improved properties was fabricated by high current pulsed electron beam (HCPEB) irradiation. The microstructure of the modified layer was investigated by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The microhardness and friction properties were also measured. After HCPEB irradiation, nano Mo particles, solid solution, and long-period superlattice structures were generated on the surface of Cu–Mo alloys, together with the formation of defect structures. These microstructures led to a significant increase in the surface hardness. The results of sliding wear tests indicated that the HCPEB-irradiated samples exhibited better properties compared with the initial one, which was attributed to the ultrafine Mo particles and the hardened surface. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the microstructure and properties of the Al Mo laser-alloyed layer induced by high-current pulsed electron beam (HCPEB) irradiation. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were utilized to investigate the microstructures of the modified layer. The microhardness and friction properties were also measured. The microstructural observation shows that HCPEB irradiation led to the formation of a modified layer approximately a dozen microns thick, which was the absence of the pores. It was found that the flower- and strip-like Al Mo particles were dissolved to form nano-size particles consisting of Al 5 Mo (h2), Al 12 Mo, and Al 17 Mo 4 phase after HCPEB irradiation. Additionally, the slip bands and high-density dislocations were formed in the modified layer. The refined microstructure significantly enhanced the microhardness of the laser-alloyed layer. A quantitative evaluation was conducted to investigate the individual contributions of four strengthening mechanisms to the strength of the modified layer, which indicated that dislocation and grain boundary strengthening were dominant. The results of sliding wear tests show that the modified layer exhibited superior properties compared to the laser alloying layer, which was attributed to the formation of crystal defects, solid solutions, and nanoparticles. • The Al-Mo laser-alloyed layer was exposed to HCPEB irradiation. • The refined precipitates and grains were formed due to the dissolution of large-sized particles. • The enhanced friction property and improved hardness are associated with increasing pulses. [ABSTRACT FROM AUTHOR]

In this paper, an Nb alloying layer on a TC4 alloy was fabricated by using high-current pulsed electron beam (HCPEB) irradiation to improve surface performance. X-ray diffraction (XRD), optical microscopy (OM), laser surface microscope (LSM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the phase composition and microstructure of the surface layer. The microhardness, wear tests and corrosion resistance were also examined. The results show that after HCPEB alloying, a Nb-alloyed layer was formed with about 3.6 μm in thickness on the surface of the sample, which was mainly composed of α'-Ti martensite, β-Ti equiaxial crystals, and NbTi4 particles. After HCPEB irradiation, the surface hardness, wear resistance and corrosion resistance of Nb alloying layer on TC4 alloy were improved compared to the initial samples. [ABSTRACT FROM AUTHOR]

In this paper, the Ni-Nb coatings were successfully prepared onto the GH3039 alloys by High current pulsed electron beam (HCPEB). The transmission electron microscopy (TEM) results confirmed that the Ni-Nb layer of 10-pulsed samples exhibited partial amorphization, which was consisted of γ-Ni particles, rod-like Ni3Nb particles and nano Ni3Nb with 30 nm in size. After 20-pulsed irradiation, the results show that only Ni3Nb clusters with around 3 nm in size were dispersed in fully amorphization layer. With increased pulse number to 30, the nano-particles embedded into the amorphous layer were grown up, the size of which was about 8 nm. The microstructure evolution during HCPEB irradiation was from the partial amorphous to fully amorphous and then to nano-crystallization. The 20-pulsed samples possessed the best hardness and corrosion resistance. The ultrafine clusters uniformly embedded into amorphous layer were main reason for improving properties. [ABSTRACT FROM AUTHOR]

In this study, the surface of a bulk crystalline Ni–Nb powder metallurgy (PM) sample of a glass-forming composition was investigated using high-current pulsed electron-beam (HCPEB) irradiation, which also improved the surface properties. Unlike the original crystalline sample, X-ray diffraction (XRD) of the surface shows an amorphous phase following HCPEB exposure. Transmission electron microscopy (TEM) reveals that, after the Ni–Nb PM samples were exposed to 20 or 30 pulses of HCPEB irradiation, the re-melted layer contains localized nanocrystalline regions within an amorphous matrix. The scanning electron microscopy (SEM) results indicate that, after 30 pulses, a re-melted layer about 5 μm in thickness forms on the surface of the Ni–Nb PM samples. Meanwhile, a large number of cracks and craters were observed on the re-melted layer. In addition, the micro-hardness tests reveal that the micro-hardness improves significantly after HCPEB irradiation. The microhardness of the sample was the highest after the 30 pulses, which was 1.5 times that of the original sample. Furthermore, potentiodynamic polarization tests indicate that the irradiated samples of corrosion resistance were not enhanced compare to the initial samples, due to the formation of cracks providing a Cl− etching channel that accelerates the corrosion rate. • The Ni–Nb amorphous alloy layer was prepared by HCPEB irradiation. • Amorphous and nanocrystalline were formed in the alloying layers. • The surface composition of the alloys gradually becomes uniform. • The microhardness and corrosion resistance were increased by HCPEB irradiation. [ABSTRACT FROM AUTHOR]

Recently, high-entropy alloys have drawn lots of attention due to their outstanding properties. In this paper, a promising new surface modification technique was acted on CoCrFeNiMo 0.2 high-entropy alloy to improve its mechanical and corrosion properties. CoCrFeNiMo 0.2 high-entropy alloys were synthesized via vacuum arc melting then, their surfaces were processed by high-current pulsed electron beam (HCPEB). Microstructure, microhardness, wear and corrosion resistance were studied systematically by means of X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Before and after HCPEB irradiation, CoCrFeNiMo 0.2 high-entropy alloy had a face-centered cubic (FCC) structure, and the surface of the irradiated samples revealed preferential orientation on the (111) and (200) planes. In addition, a compact and homogenization surface layer formed after irradiation. Also, high-amplitude stress caused high-density dislocations and stacking faults on the surface. After HCPEB irradiation, the properties of the samples were significantly improved, the maximum microhardness (392.9 HV) and lowest wear rate (0.92 × 10−4 mm3·N−1·m−1) was obtained after 35-pulsed irradiation. Furthermore, corrosion resistance was obviously enhanced after 25-pulsed irradiation. [Display omitted] • HCPEB irradiation was conducted on the surface of as-cast CrFeCoNiMo 0.2 high entropy alloy. • A 3-8 μm thick compact remelted layer was formed after irradiation and the equiaxed grains along with σ phase were refined with the increase of the pulses. • Abundant structure defects such as subcrystals, high-density dislocations, dislocation cells, and stacking faults were also formed due to thermal stress induced by irradiation, resulting in intense plastic deformation of the material surface. • Surface microhardness, tribological behavior and corrosion resistance were improved due to grain refinement and compositional homogenization. [ABSTRACT FROM AUTHOR]