Effect of Ti Content on the Microstructure and Corrosion Resistance of CoCrFeNiTix High Entropy Alloys Prepared by Laser Cladding

Abstract

In this paper, CoCrFeNiTix high entropy alloy (HEA) coatings were prepared on the surface of Q235 steel by laser cladding. The microstructure, microhardness, and corrosion resistance of the coatings were studied. The mechanism of their corrosion resistance was elucidated experimentally and by first-principles calculations. The results show that CoCrFeNiTi0.1 adopts a face-centered cubic (FCC) phase, CoCrFeNiTi0.3 exhibits an FCC phase and a tetragonal FeCr phase, and CoCrFeNiTi0.5 adopts an FCC phase, a tetragonal FeCr phase, and a rhombohedral NiTi phase. The FCC phase, tetragonal FeCr phase, rhombohedral NiTi phase, and hexagonal CoTi phase are all observed in the CoCrFeNiTi0.7 HEA. The alloys assume the dendritic structure that is typical of HEAs. Ni and Ti are enriched in the interdendritic regions, whereas Cr and Fe are enriched in the dendrites. With increasing Ti content, the hardness of the cladding layers also increases due to the combined effects of lattice distortion and dispersion strengthening. When exposed to a 3.5 wt.% NaCl solution, pitting corrosion is the main form of corrosion on the CoCrFeNiTix HEA surfaces. The corrosion current densities of CoCrFeNiTix HEAs are much lower than those of other HEAs. As the Ti content increases, the corrosion resistance is improved. Through X-ray photoelectron spectroscopy (XPS) and first-principles calculations, the origin of the higher corrosion resistance of the coatings is connected to the presence of a dense passivation film. In summary, the corrosion resistance and mechanical properties of CoCrFeNiTi0.5 alloy are much better than the other three groups, which promotes the development of HEA systems with high value for industrial application.

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

“…In the majority of cases, multicomponent alloys are synthesized by crystallization from the melt (arc or induction melting in vacuum or argon [5][6][7][13][14][15][16][17][18][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43], plasma spark sintering [19], electric current assisted sintering [20,21], laser or plasma cladding deposition of coatings [44][45][46][47][48][49][50][51][52][53][54][55], additive manufacturing by the laser-powder bed fusion [56,57] or laser-metal deposition [58], self-propagating high-temperature synthesis (SHS) [59], and by brazing within the brazing joints [60,61]). Figure 1 shows a schematic phase diagram for the simplest case when there are on...…”

Grain Boundary Wetting by a Second Solid Phase in the High Entropy Alloys: A Review

“…In the majority of cases, HEAs are manufactured by crystallization from the melt after arc or induction melting [5][6][7][8][9][10][11][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34], electric current assisted sintering [35,36], plasma spark sintering [37], additive manufacturing by the laser powder bed fusion [38,39] or laser metal deposition [40], laser or plasma cladding deposition of coatings [41][42][43][44][45][46][47][48][49][50][51][52], selfpropagating high-temperature synthesis (SHS) [53], or even by brazing of dissimilar materials within the brazing joints [54,55]). In some cases, the liquid phase is not present during the synthesis of HEAs such as in the case of sputter deposition of coatings…”

Research Progress of Titanium-Based High Entropy Alloy: Methods, Properties, and Applications

“…In order to study the effect of the Ti element on the wear resistance of the coating prepared by laser cladding, Wang X. et al (2020) studied CoCrFeNiTix HEA coatings with different Ti content and found that the hardness and corrosion resistance of the coatings increased with the addition of Ti content. Furthermore, the main corrosion mechanism of CoCrFeNiTix high entropy coatings in 3.5wt% NaCl solution is pitting corrosion.…”