A comparison of the dry sliding wear behavior of NiCoCr medium entropy alloy with 316 stainless steel
Introduction
The equi-atomic NiCoCr medium entropy alloy exhibits an extremely high room temperature fracture toughness above 200 MPa m1/2, as demonstrated by Gludovatz et al. [1]. The alloy, which is a single-phase f.c.c. solid solution, shows even better strength and ductility with decreasing temperature. Indeed, the alloy shows a good balance of strength and ductility over the temperature range from −196 °C to 400 °C [[1], [2], [3]], while the results of fracture toughness tests showed that the NiCoCr medium-entropy alloy represents one of the toughest materials in any materials class ever reported [1].
There have been several studies of the room temperature wear behavior of both bulk high entropy alloys (HEAs) and HEA coatings [[4], [5], [6], [7]], which have generally been of the sliding pin-on-disk type conducted at room temperature in air. Tsai and Yeh [8] discussed the wear properties of HEAs and noted that the wear resistance of f.c.c. single-phase HEAs increased with increasing hardness, a well-known feature referred to as the Archard law [9,10], i.e.where W is the volume loss of materials through wear, K is the wear coefficient, F is the normal load, L is the sliding distance, and H is the hardness of the material. Tsai and Yeh [8] found that HEAs containing an ordered second phase had improved wear resistance, especially if the second phase was hard and was the majority phase. Thus, compared to the wear behavior of 52100 (SUJ2) bearing steel, the wear resistance of the HEA Al0.2Co1.5CrFeNi1.5Ti is 3.6 times better, even though these two materials have similar hardness values [4]. Similarly, the HEA Co1.5CrFeNi1.5Ti has a wear resistance comparable to that of H13 tool steel even though the hardness of H13 steel is greater [4]. Very recent wear testing of NiCoCr against an Inconel 718 counterpart at elevated temperatures found much lower wear rates at higher sliding temperatures, and concluded that the wear mode changes from abrasive wear at room temperature to oxidative and adhesive wear at 200 °C. However, the authors of [11] didn't investigate the important effect of environment on the wear rate of the materials and didn't consider the contribution of frictional heating to the contact temperature during sliding wear tests.
Sliding contact produces substantial heating during the wear tests as energy is transformed from the friction force, which results in a temperature increase of the contact area of the pins [12]. The temperature increase can influence the pin's hardness and make plastic deformation in the pin/disk contact area much easier. The wear rate also changes with hardness according to Eq. (1). This temperature increase can also lead to greater oxidation of the pin tip. In iron-based metals, it is thought that an oxide film forms on the surface that could increase the wear resistance [13]. Although an oxide could work as protection of the metallic surface during wear, it may break off to produce wear particles, i.e. wear debris [14]. When wear tests are performed at a slow speed and limited load with the contact temperature lower than 400 °C, the oxides in iron-based alloys are usually soft and part of the oxide film spalls to produce mild oxidative wear [14]. If the wear debris is much harder than the metal layer, it could lead to severe wear, which has been found in NiAl-based alloys [15].
This work is a study of the wear behavior of equi-atomic NiCoCr using pin-on-disk sliding wear tests against an yttria-stabilized zirconia (YSZ) disk in both air and argon. These results are compared with those from similar tests performed on 316 stainless steel, which is a single-phase austenitic alloy that exhibits good oxidation and corrosion resistance at relatively low cost and is used in numerous applications, despite its suboptimal wear resistance. It is of interest to study if the higher yield strength of NiCoCr compared to 316 stainless steel will produce better wear resistance.
Section snippets
Materials and methods
An ingot of equi-atomic NiCoCr alloy was prepared by arc-melting elemental Ni, Co and Cr (purities >99.9%) under argon. The ingot was melted three times and flipped to another face before the next melting to ensure homogeneity. The alloy was then placed in a Bridgeman furnace and a rod 71 mm long and 12 mm diameter was produced. Both the NiCoCr rod and a commercial 10 mm diameter 316 stainless steel rod were machined into pins 19 mm long, 9.5 mm diameter with hemispherical tips. All pins were
The wear behavior of NiCoCr alloys and 316 stainless steel pins
The results from wear tests of NiCoCr alloys and 316 stainless steel pins performed against YSZ disks at room temperature in air and argon are shown in Fig. 1. Three tests were conducted to obtain the average wear rates of each alloy under the different atmospheres and to calculate the error bars. The two materials both have much greater mass loss after wear tests in air compared to tests under argon. The NiCoCr pins had an average mass loss of 31 mg in air and 4.9 mg in argon, while the 316
Discussion
The results in Fig. 1 indicated that the mass loss of the NiCoCr pins during wear tests against YSZ was less than that for 316 stainless steel pins, especially in air. This may be partially attributed to the higher hardness of the NiCoCr material, as predicted by the Archard law. The material's toughness can also influence its wear performance, particularly through its influence on abrasion. The failure strain of NiCoCr alloys during tensile tests at room temperature is 70% [1], while this
Summary
Dry sliding pin-on-disk wear tests of NiCoCr alloy against yttria-stabilized zirconia were conducted in air and argon and the results compared to tests on 316 stainless steel. The results and comparison indicate that:
1. The wear rate of the NiCoCr pins in air at 0.1 m/s velocity was much lower than the wear rate of the 316 stainless steel: the wear rates of the NiCoCr and the 316 stainless steel under argon were similar and much lower than the wear rates in air.
2. The worn surfaces of NiCoCr
Declaration of competing interest
There is no conflict of interest.
Acknowledgements
This work was supported by National Science Foundation grant number 1758924.
References (20)
- et al.
Recovery, recrystallization, grain growth and phase stability of a family of FCC-structured multi-component equiatomic solid solution alloys
Intermetallics
(2014) - et al.
Temperature dependence of the mechanical properties of equiatomic solid solution alloys with face-centered cubic crystal structures
Acta Mater.
(2014) - et al.
Microstructure and wear behavior of AlxCo1.5CrFeNi1.5Tiy high-entropy alloys
Acta Mater.
(2011) - et al.
Effect of Nb addition on the structure and mechanical behaviors of CoCrCuFeNi high-entropy alloy coatings
Surf. Coat. Technol.
(2014) - et al.
Microstructure and wear behavior of a refractory high entropy alloy
Int. J. Refract. Met. Hard Mater.
(2016) The role of oxidation in the wear of alloys
Tribol. Int.
(1998)The mechanism of oxidational wear
Wear
(1995)- et al.
Dry sliding wear of NiAl
Wear
(1996) - et al.
Thermophysical properties of Ni-containing single-phase concentrated solid solution alloys
Mater. Des.
(2017) Comments on the sliding wear of metals
Tribology Int
(1997)
Cited by (12)
Review on the preparation methods and strengthening mechanisms of medium-entropy alloys with CoCrNi as the main focus
2023, Journal of Materials Research and TechnologyCharacterisation and property evaluation of High Entropy Alloy coating on 316L steel via thermal spray synthesis
2023, Tribology InternationalInvestigation of microstructure and wear resistance of laser-clad CoCrNiTi and CrFeNiTi medium-entropy alloy coatings on Ti sheet
2022, Optics and Laser TechnologyCitation Excerpt :In this work, pulsed laser cladding was employed to prepare two MEACs (CoCrNiTi and CrFeNiTi) on a high-purity Ti sheet to obtain improved surface properties. The compositions of our coatings are determined after referencing those of CoCrNi and CrFeNi ternary MEAs [12–15] with additional Ti diluted from the substrate. As demonstrated in Ref. [22], further improved hardness and wear resistance could be expected by adding Ti into such ternary MEAs.
Non-metal group doped g-C<inf>3</inf>N<inf>4</inf> combining with BiF<inf>3</inf>:Yb<sup>3+</sup>, Er<sup>3+</sup> upconversion nanoparticles for photocatalysis in UV–Vis–NIR region
2021, Colloids and Surfaces A: Physicochemical and Engineering AspectsCitation Excerpt :Nowadays, the increasing serious environmental problems have prompted much research in the field of photocatalysis [1]. In the past few decades, a large number of semiconductor photocatalysts have been exploited for environmental application [2–7]. In order to improve the efficiency of photocatalysis, people usually prepare composite photocatalysts for photocatalysis.
Tuning the mechanical and high temperature tribological properties of Co-Cr-Ni medium-entropy alloys via controlling compositional heterogeneity
2021, Journal of Alloys and CompoundsCitation Excerpt :On the other hand, it is also of great value to explore the response of operational parameters (e.g., composition, temperature, atmosphere and counterpart) on the tribochemical behaviors of the CoCrNi MEAs and to reveal the wear mechanism. Baker et al. [18] compared the tribological performances of CoCrNi MEA and 316 stainless steel in air and argon respectively. The wear-resistance of the former is superior to that of the latter in air due to the formation of a mechanically tribo-layer, yet they show similar wear rates in argon.