Investigation on annealing strengthening effect of laser cladding Fe5Cr5Co5SiTiNbMoW high-entropy alloy coating
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ARTICLE Investigation on annealing strengthening effect of laser cladding Fe5Cr5Co5SiTiNbMoW high-entropy alloy coating Yaxiong Guo and Qibin Liua) College of Materials and Metallurgy, Guizhou University, Guiyang 550025, People’s Republic of China
Xiaojuan Shang Department of Mechanical and Electronic, Guizhou Jiaotong Technical School, Guiyang 550025, People’s Republic of China (Received 4 June 2018; accepted 21 August 2018)
To improve the high-temperature properties of tool steel, a microstructure-dense and crack-free Fe5Cr5Co5SiTiNbMoW high-entropy alloy (HEA) coating was successfully fabricated by laser cladding. And its microstructure and hardness evolution after various annealing temperatures of 800 °C, 850 °C, 950 °C, and 1050 °C for 4 h were carefully investigated by OM, scanning electron microscope, energy dispersion spectrum, X-ray diffraction, and microhardness tester, respectively. The experimental results show that the HEAcoating was mainly composed of body-centered cubic and (Nb, Ti)C plus few Laves phase. The high-temperature annealing processing has little influence on the phase composition. The dendrites and matrix are decomposed with the annealing temperature increasing. While annealing at 950 °C, a eutectic microstructure appeared in the coating. Moreover, the thickness of the diffusion layer of HEA coating increased with the increasing of annealing temperatures. Surprisingly, the HEA coating after annealing at 850 °C possessed ultra-high average hardness, about 1050 HV0.2, huge improvement compared with as-cladding HEA coating (;780 HV0.2). Therefore, it might reveal that the HEA coating exhibits excellent annealing strengthening ability.
I. INTRODUCTION
The extensive applications of high-speed-cutting machines and materials difficult to process could raise extremely strict requirements for excellent red hardness and wear resistance of cutting tools.1 Normally, commercial Fe-based tool steels could not be suitable for the meets of high-speed cutting or dry cutting. TiN, TiC hard ceramic films with ultra-high hardness synthesized on tool steels could prolong service life and improve cutting efficiency.2 However, the disadvantages of hard ceramic film including high residual stress, thin thickness, and weak bonding with substrate could seriously limit the wide industrial application in high-speed cutting.3 High-entropy alloys (HEAs), first proposed in 2004, have been drew great attention in metallic materials science and engineering because of their excellent mechanical performances.4 It is remarkably considered that HEAs could be one of the three research directions in metallic field.5 Owing to the high-entropy effect in thermodynamics, the explored HEAs could be classified by main phase structures into three groups: face-centered cubic (FCC),6 body-centered cubic (BCC),7 and hexagonal close-packed8 structures plus a few intermetallic
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2018.330 J. Mater. Res., 2018
compounds.9 Multiple alloy elements with atomic
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