Microstructure Evolution and Properties of Laser Cladding CoCrFeNiTiAlx High-Entropy Alloy Coatings

Abstract

High-entropy alloy (HEA) coatings of CoCrFeNiTiAlx (x = 0, 0.5, 1, 1.5, 2) were prepared on the surface of AISI1045 steel by laser cladding. The effects of the Al content on the microstructure, composition, phase constitution, and wear and corrosion resistance of the coatings were investigated. The results showed that when increasing the Al element content from 0 to 0.5, the phase constitution of the CoCrFeNiTiAlx coating changed from a single Face-centered cubic (FCC) phase to Body-centered cubic 1 (BCC1) and Body-centered cubic 2 (BCC2) phases, with a small amount of Laves phase, which obviously improved the friction and corrosion resistance of the coating. With further enhancing of the Al content, the amount of BCC1 phase increased, while the BCC2 phase and the Laves phase decreased. The CoCrFeNiTiAl2 HEA coating transformed into a single BCC1 phase, with retrogressive wear and corrosion resistance. It was found that the Al0.5 alloy coating exhibits excellent wear resistance, high hardness, and corrosion resistance in a 3.5 wt.% NaCl solution. Furthermore, the effect of the Al content on the microstructure, phase, and the relating properties of the CoCrFeNiTiAlx HEA coatings is also discussed.

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...…”

Wear and Corrosion Resistance Analysis of FeCoNiTiAlx High-Entropy Alloy Coatings Prepared by Laser Cladding

“…The segregation of elements is related to the mixing enthalpies between elements. The smaller the enthalpy of mixing, the greater the affinity between the two elements [16]. According to Table 7, the mixing enthalpy between the Fe element and the other four elements is high, so the affinity is relatively weak.…”

“…Therefore, when the applied potential moves towards the anode, the grain boundaries have higher dislocation density and corrosion activity. So they are more susceptible to corrosion damage, which will promote the corrosion of the coating, and cause the corrosion current density to increase [16]. With the further increase of Al element, the self-corrosion potential of Al 1 coating is obviously shifted to the anode direction than that of Al 0.5 coating, indicating that its corrosion resistance has improved a lot.…”

“…By adding Al, Ti, Mo and other elements with larger atomic radius to the coating, the hardness and wear resistance of the coating will be significantly improved. Xu et al [16] prepared CoCrFeNiTiAl x high-entropy alloy coating by laser cladding. The results showed that the addition of Al improves the hardness and wear resistance of the coating, and at the same time improves the corrosion resistance in 3.5% NaCl solution.…”

Recent Advances of High Entropy Alloys: High Entropy Superalloys

“…Nevertheless, these lasers are limited in applications because they require a large volume of organic solvents for efficiency. Xu et al [108] used a laser stimulated fluorescence equipment consisting of an organic liquid dye to fabricate a HEA and study the performance of the coatings then the influence of aluminum on the properties of the alloy. The authors stated that the laser technology and the aluminum content enabled the phase transitions, grain refinement and corrosion resistance observed.…”