On the enhanced wear resistance of CoCrFeMnNi high entropy alloy at intermediate temperature

In this review, the phenomenon of grain boundary (GB) wetting by melt is analyzed for multicomponent alloys without principal components (also called high-entropy alloys or HEAs) containing titanium. GB wetting can be complete or partial. In the former case, the liquid phase forms the continuous layers between solid grains and completely separates them. In the latter case of partial GB wetting, the melt forms the chain of droplets in GBs, with certain non-zero contact angles. The GB wetting phenomenon can be observed in HEAs produced by all solidification-based technologies. GB leads to the appearance of novel GB tie lines Twmin and Twmax in the multicomponent HEA phase diagrams. The so-called grain-boundary engineering of HEAs permits the use of GB wetting to improve the HEAs’ properties or, alternatively, its exclusion if the GB layers of a second phase are detrimental.

The Grain Boundary Wetting Phenomena in the Ti‐Containing High‐Entropy Alloys: A Review

The influence of Nb doping on the structure evolution, hardness and wear behaviors of laser-cladded (Fe0.25Co0.25Ni0.25(B0.7Si0.3)0.25)100-xNbx (denoted as Nbx hereafter, x = 0, 1, 2, 3 and 4 at.%) high entropy alloy coatings were analyzed. Detailed characterization indicated that the microstructures evolve from face-centered cubic (FCC) and (Fe, Co, Ni)2B phases of the Nb-free coating to FCC, (Fe, Co, Ni)2B and amorphous phases of the Nb-containing coating (1 ≤ x ≤ 2). Notably, the glass formation ability of the coating is enhanced with the addition of Nb. As the Nb content further increases (3 ≤ x ≤ 4), it promotes the fully crystalline structures of body-centered-cubic (BCC), Laves, FCC and (Fe, Co, Ni)2B phases. The average crystalline size of the coating is refined from 3.5 to 1.3 μm as a function of Nb content. The wear resistance of the coatings improves firstly and then aggravates with increasing of Nb content, which corresponds to the variation trend of microhardness and microstrain. The Nb2 coating shows a maximum hardness value of 11.9 Gpa and excellent wear resistance due to the formation of amorphous structure and good elastic properties. The phase prediction in the coating was calculated by thermodynamic parameters. The relationships between the structure and properties of the present coating were elucidated. The new metal-metalloid high entropy metallic glassy coating and superior properties give its good promise for engineering applications.

Nb doping in laser-cladded Fe25Co25Ni25(B0.7Si0.3)25 high entropy alloy coatings: Microstructure evolution and wear behavior

Design and development of TiC-reinforced 410 martensitic stainless steel coatings fabricated by laser cladding

A review on the steels, alloys/high entropy alloys, composites and coatings used in high temperature wear applications

(CoCrFeMnNi)85Ti15 high-entropy alloy (HEA) coating prepared on Q235 steel substrate via plasma cladding was investigated for its microstructure, hardness, and high temperature tribological performance. The microstructure of (CoCrFeMnNi)85Ti15 HEA consists of FCC and BCC solid solutions as well as an intermetallic sigma phase. The FCC solid solution is characterized by a lattice parameter of 3.669 A and is enriched with Co-Cr, the BCC solid solution has a lattice parameter of 2.998 A and is enriched with Fe-Mn, and the intermetallic sigma phase is enriched with Ni-Ti. The micro-hardness of the Q235 steel substrate, the CoCrFeMnNi HEA coating, and the (CoCrFeMnNi)85Ti15 HEA coating is 123.6 ± 6.2, 150.1 ± 7.4, and 910.5 ± 26.6 HV, respectively. As the hardness of the (CoCrFeMnNi)85Ti15 HEA coating is enhanced six times more than that of the CoCrFeMnNi HEA coating, it exhibits a lower wear rate and a better wear resistance at high temperatures. The best wear resistance, which corresponds to a wear rate of 4.08 × 10−6 mm3·N−1·m−1, is obtained at 400 °C. The wear mechanisms of the (CoCrFeMnNi)85Ti15 HEA coating are predominantly oxidation wear and contact fatigue, although there is evidence of oxidation wear and adhesive wear at 800 °C.

Study of high temperature friction and wear performance of (CoCrFeMnNi)85Ti15 high-entropy alloy coating prepared by plasma cladding

Ti content effect on microstructure and mechanical properties of plasma-cladded CoCrFeMnNiTix high-entropy alloy coatings

In this paper, thermal oxidation was used to prepare an oxide layer on a pure titanium surface using the equal-channel angular pressing (ECAP) treatment. Transmission electron microscopy, field emission scanning electron microscopy, X-ray diffraction and Raman spectrometry were used for morphology and structure characterization and investigation of the oxidation kinetics during the oxidation process. The results showed that the major phase of the oxide layer was rutile-type TiO2. The presence of voids in the oxide layer decreased with increasing temperature. The grain size of the TiO2 obtained on the ECAP-treated Ti surface was smaller than that on the as-received titanium. The ECAP treatment promoted the formation of the oxide layer; the activation energy (Q) for the oxidation reaction with ECAP treatment was 81.03 kJ mol−1 in the range of 650 °C to 850 °C, which was 26.3% lower than that of the as-received titanium. The hardness values of the oxide layers on the as-received titanium and ECAP-treated Ti were 705.8 HV and 805.1 HV, respectively. The friction coefficient of the oxide layer on the ECAP-treated Ti was lower than that on the as-received titanium. The wear rates of the oxide layers on the ECAP-treated Ti and as-received titanium were 4.66 × 10−8 mm3 N−1 m−1 and 6.28 × 10−8 mm3 N−1 m−1, respectively.

Effects of ECAP on the Formation and Tribological Properties of Thermal Oxidation Layers on a Pure Titanium Surface

The gradient fine-grained oxygen-boosting layer was prepared on equal channel angular processing (ECAP)-treated titanium with thermal oxidation and oxygen boost diffusion process, and tribological ...

Jiying Wang

Papers

Study of high temperature friction and wear performance of (CoCrFeMnNi)85Ti15 high-entropy alloy coating prepared by plasma cladding

Ti content effect on microstructure and mechanical properties of plasma-cladded CoCrFeMnNiTix high-entropy alloy coatings

Effects of ECAP on the Formation and Tribological Properties of Thermal Oxidation Layers on a Pure Titanium Surface

Fabrication and Tribological Properties of Gradient Fine-Grained Oxygen-Boosting Layer on Ecap-Treated Pure Titanium Surface