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Microstructure and mechanical properties of borided CoCrFeNiAl0.25Ti0.5 high entropy alloy produced by powder metallurgy.

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Title: Microstructure and mechanical properties of borided CoCrFeNiAl0.25Ti0.5 high entropy alloy produced by powder metallurgy.
Authors: Erdogan, Azmi1 (AUTHOR) aerdogan@bartin.edu.tr, Günen, Ali2 (AUTHOR), Gök, Mustafa Sabri3 (AUTHOR), Zeytin, Sakin4 (AUTHOR)
Source: Vacuum. Jan2021, Vol. 183, pN.PAG-N.PAG. 1p.
Subjects: Powder metallurgy, Alloy powders, Boriding, Microstructure, Fracture toughness, Titanium powder
Abstract: CoCrFeNiAl 0.25 Ti 0.5 high entropy alloy alloys (HEA), produced by powder metallurgy were subjected to boriding to improve their mechanical properties. Sintering was carried out at 1200 °C for 2 h in Ar, and boriding was performed at 900, 1000 and 1100 °C for 2 h using a 90 wt% B 4 C + 10 wt% NaBF 4 boriding powder mixture. Microstructures, densities, surface roughnesses, and mechanical properties (hardness, fracture toughness and nanoindentation responses) of the samples were investigated. FCC, BCC and sigma phases had been observed after sintering, whereas complex metal borides were formed on the surfaces after boriding. Relative density values were between 85% and 90%. Significant increases in surface hardness were observed after boriding due to formation of hard, silicide-free boride layers. The boride layer thickness and hardness increased with increasing boriding temperature. The elastic modulus of the surface of the sintered sample (47.07 GPa) increased with the boriding process to values in the range of 140–151 GPa. Fracture toughness values between 3.57 and 4.25 MPa m1/2 were obtained in borided samples, and increasing the boriding temperature reduced the fracture toughness. • P/M produced CoCrFeNiAl 0.25 Ti 0.5 high entropy alloy was successfully borided. • Density, roughness, hardness, fracture toughness, etc. Properties were examined. • 255–363 μm thickness coating layer was obtained in the borided samples. • The 531 H V microhardness value increased to 1461–1646 by boriding. • The fracture toughness values of the boride layer were between 3.57 and 4.25 MPa m1/2. [ABSTRACT FROM AUTHOR]
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Abstract:CoCrFeNiAl 0.25 Ti 0.5 high entropy alloy alloys (HEA), produced by powder metallurgy were subjected to boriding to improve their mechanical properties. Sintering was carried out at 1200 °C for 2 h in Ar, and boriding was performed at 900, 1000 and 1100 °C for 2 h using a 90 wt% B 4 C + 10 wt% NaBF 4 boriding powder mixture. Microstructures, densities, surface roughnesses, and mechanical properties (hardness, fracture toughness and nanoindentation responses) of the samples were investigated. FCC, BCC and sigma phases had been observed after sintering, whereas complex metal borides were formed on the surfaces after boriding. Relative density values were between 85% and 90%. Significant increases in surface hardness were observed after boriding due to formation of hard, silicide-free boride layers. The boride layer thickness and hardness increased with increasing boriding temperature. The elastic modulus of the surface of the sintered sample (47.07 GPa) increased with the boriding process to values in the range of 140–151 GPa. Fracture toughness values between 3.57 and 4.25 MPa m1/2 were obtained in borided samples, and increasing the boriding temperature reduced the fracture toughness. • P/M produced CoCrFeNiAl 0.25 Ti 0.5 high entropy alloy was successfully borided. • Density, roughness, hardness, fracture toughness, etc. Properties were examined. • 255–363 μm thickness coating layer was obtained in the borided samples. • The 531 H V microhardness value increased to 1461–1646 by boriding. • The fracture toughness values of the boride layer were between 3.57 and 4.25 MPa m1/2. [ABSTRACT FROM AUTHOR]
ISSN:0042207X
DOI:10.1016/j.vacuum.2020.109820