skip to main content

Explore Research Products in the NSF-PAR

Title: Tribo-corrosion response of additively manufactured high-entropy alloy
Abstract High-entropy alloys (HEAs) with multiple principal elements represent a paradigm shift in structural alloy design and show excellent surface degradation resistance in corrosive environment. Here, the tribo-corrosion response of laser-engineered net-shaped CoCrFeMnNi HEA was evaluated in 3.5 wt% NaCl solution at room temperature. The additively manufactured (AM-ed) CoCrFeMnNi showed five times lower wear rate, regenerative passivation, and nobler corrosion potential during tribo-corrosion test compared to its arc-melted counterpart. A significant anisotropy was seen in the tribo-corrosion response with 45° to the build direction showing better performance compared to tests along the build direction and perpendicular to it. The open circuit potential curves were characterized by a sharp drop to more negative values as wear began, followed by continuous change for the active tribo-corrosion duration and finally a jump to nobler value at the end of the test indicating excellent surface re-passivation for the AM-ed alloy. The superior tribo-corrosion resistance of AM-ed CoCrFeMnNi was attributed to the refined microstructure and highly protective surface passivation layer promoted by the sub-grain cellular structure formed during additive manufacturing. These results highlight the potential of utilizing additive manufacturing of HEAs for use in extreme environments that require a combination of tribo-corrosion resistance, mechanical durability, extended service life, and net shaping with low dimensional tolerance.  more » « less
Award ID(s):
2004429
NSF-PAR ID:
10281475
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ;
Date Published:
Journal Name:
npj Materials Degradation
Volume:
5
Issue:
1
ISSN:
2397-2106
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ( , Materials letters)
    null (Ed.)
    Processing and characterization for zirconia toughened alumina (ZTA) coatings on Ti6Al4V (Ti64) alloy by directed energy deposition (DED)-based additive manufacturing (AM) is presented here. The objective of the study was to achieve a dense ZTA coating with the intent of providing an alternative to fully ceramic implants for articulating surfaces of total hip arthroplasty (THA). Preliminary work resulted in failed samples due to cracking, porosity, and delamination. After careful parameter optimization, a Ti64+5wt.%ZTA (5ZTA) composition produced a metallurgically sound and coherent coating with minimal porosity. Additionally, bulk structures were also feasible with the optimized coating parameters. Characterization of the 5ZTA composition displayed a 27.0% increase in hardness, 25% reduction in normalized wear rate, an increase in contact resistance during in vitro tribological testing along with a faster surface re-passivation post-tribological testing. 
    more » « less
  2. ; ; ; ( , Additive manufacturing)
    "Binder jetting is an economical and rapid additive manufacturing process that offers vast opportunities to combine a variety of materials, yielding interesting and useful properties. However, binder jetted parts, which can involve at least one hard and one soft material, can be more susceptible to corrosion and wear compared to conventional single alloy components produced by laser sintering or other high-temperature processes. This paper discusses the electroless nickel coating on 420 Stainless Steel and Bronze Binder-Jetted Composites(BJC). Electroless nickel, a well-known coating to provide high corrosion resistance and hardness, was attempted on BJC. To produce high-quality smooth electroless nickel coatings, we attempted the Taguchi Design of Experiments. Our design of experiment involved important factors, such as the surface preparation methodology prior to electroless nickel coating. During electroless nickel coating, we investigated the role of phosphorus content, temperature, and time in the production of smooth deposition. Optical microscopy was performed for qualitative and quantitative analysis. We also performed SEM to investigate the microstructure of different electroless coatings on BJC. Interestingly, all the combinations of parameters used in the electroless nickel coating produced different microstructures. We found that surface preparation was a critical factor in determining the smoothness of the film. We also showed that the dependent on the Ni solution’s phosphorus level and temperature. Our research ng insights for improving the usefulness of a wide variety of BJC by various coatings." 
    more » « less
  3. ; ; ; ; ( , Journal of The Electrochemical Society)

    Exposure testing was performed on CoCrFeMnNi equiatomic high entropy alloy (HEA) produced via directed energy deposition additive manufacturing in NaNO3-KNO3(60–40 wt%) molten salt at 500 °C for 50 h to evaluate the corrosion performance and oxide film chemistry of the HEA. Potentiodynamic electrochemical corrosion testing, scanning electron microscopy, focused ion beam milling coupled with energy dispersive spectroscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and inductively coupled plasma optical emission spectroscopy were used to analyze the corrosion behavior and chemistry of the HEA/nitrate molten salt system. The CoCrFeMnNi HEA exhibited a higher passive current density during potentiodynamic polarization testing than steel alloys SS316L and 4130 and the high-Ni alloy 800 H in identical conditions. The oxide film was primarily composed of a (Mn,Co,Ni)Fe2O4spinel with a vertical plate-like morphology at the surface. Cr and Ni were found to be totally depleted at the outer surface of the oxide and dissolved in high concentrations in the molten salt. While Cr was expected to dissolve into the molten salt, the high concentration of dissolved Ni has not been observed with traditional alloys, suggesting that Ni is less stable in the spinel when Mn and Co are present.

     
    more » « less
  4. ; ; ; ; ; ; ( , Coatings)
    null (Ed.)
    In this study, a compact cold sprayed (CS) Ti coating was deposited on Mg alloy using a high pressure cold spray (HPCS) system. The wear and corrosion behavior of the CS Ti coating was compared with that of CS Al coating and bare Mg alloy. The Ti coating yielded lower wear rate compared to Al coating and Mg alloy. Electrochemical impedance spectroscopy (EIS) and cyclic potentiodynamic polarization (CPP) tests revealed that CS Ti coating can substantially reduce corrosion rate of AZ31B in chloride containing solutions compared to CS Al coating. Interestingly, Ti-coated Mg alloy demonstrated negative hysteresis loop, depicting repassivation of pits, in contrast to AZ31B and Al-coated AZ31B with positive hysteresis loops where corrosion potential (Ecorr) > repassivation potential (Erp); indicating irreversible growth of pits. AZ31B and Al-coated AZ31B were most susceptible to pitting corrosion, while Ti-coated Mg alloy indicated noticeable resistance to pitting in 3.5 wt % NaCl solution. In comparison to Al coating, Ti coating considerably separated the AZ31BMg alloy surface from the corrosive electrolyte during long term immersion test for 11 days. 
    more » « less
  5. ; ; ( , Metals)
    High-entropy alloys (HEAs) prefer to form single-phase solid solutions (body-centered cubic (BCC), face-centered cubic (FCC), or hexagonal closed-packed (HCP)) due to their high mixing entropy. In this paper, we systematically review the mechanical behaviors and properties (such as oxidation and corrosion) of BCC-structured HEAs. The mechanical properties at room temperature and high temperatures of samples prepared by different processes (including vacuum arc-melting, powder sintering and additive manufacturing) are compared, and the effect of alloying on the mechanical properties is analyzed. In addition, the effects of HEA preparation and compositional regulation on corrosion resistance, and the application of high-throughput techniques in the field of HEAs, are discussed. To conclude, alloy development for BCC-structured HEAs is summarized. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email