Tribological characterization of an alumina-based composite in dry sliding contact against laser-heated and unheated Inconel 718

https://doi.org/10.1016/j.triboint.2020.106773Get rights and content

Highlights

  • We studied tribology of a new Al2O3-based ceramic in dry sliding against Inconel 718.

  • We carried out two sets of experiments under laser-heated and unheated conditions.

  • We described the formation mechanism of tribochemical layers at high velocities.

  • We analyzed the influence of TiC nanoparticles in lowering the wear rate.

Abstract

Alumina-based ceramic tools have been successfully applied in high-speed turning of superalloys. In this study, the tribological characteristics of a novel Al2O3-SiCw-TiCn ceramic composite were investigated in unlubricated sliding contact against laser-heated (600 °C) and unheated Inconel 718 between 2.5 m/s and 10 m/s. The tribological behavior of the Al2O3-SiCw-TiCn ceramic was compared to a commercial Al2O3-SiCw ceramic. The results indicated similar coefficients of friction (COF) in laser-heated and unheated tests. Below 7.5 m/s, the wear mechanisms in laser-heated tests were brittle fracture, plastic flow and adhesive wear and predominantly brittle fracture in unheated tests. A tribochemical layer mainly containing chromium and oxygen has formed on the contact surface at 10 m/s resulting in lowering the COF and reducing wear.

Introduction

Advanced ceramics have clear advantage in high temperature applications due to their exceptional high-temperature properties. For example, alumina (Al2O3) and silicon nitride (Si3N4) based ceramics have been successfully used as high temperature wear-resistant parts [[1], [2], [3]] or as cutting insets in high-speed machining (HSM) of difficult-to-cut alloys [[4], [5], [6]]. Al2O3 based ceramics reinforced with silicon carbide whiskers (SiCw) are well known to be used in HSM of nickel-based alloys [7,8]. In addition, these advanced ceramic tools have shown a great potential in laser-assistant machining (LAM) of difficult-to-cut alloys. Anderson et al. [9] and Ding et al. [10] studied the tool wear of a Greenleaf WG-300 insert, which is a SiCw toughened Al2O3 ceramic tool (Al2O3-SiCw), in LAM of nickel-based alloys at cutting speeds of 2 m/s and 2.2 m/s. The material removal temperature Tmr ranged from 300 °C to 540 °C. In both studies it was found that both flank wear and notch wear decreased in LAM compared to that in conventional machining, while the average flank wear increased with the increasing of Tmr. Germain et al. [11] used a similar ceramic insert (CC670, Sandvik) to study the LAM of Inconel 718 at a speed of approx. 3.7 m/s. The authors reported an improvement of 25% in the lifetime of ceramic tools in LAM in comparison to conventional machining. Nonetheless, with increasing cutting time, the tool wear in LAM becomes greater. LAM can improve the workability of nickel-based alloys and improve the integrity of the machined surface. However, when using SiCw toughened Al2O3 ceramic tools to machine nickel-based alloys, the optimal speed in LAM is lower than that in dry and HSM [11,12].

Pin-on-disk tests are a well-established method to investigate the tribological behavior of materials and can provide basic knowledge to guide in the selection of materials as well as proper cutting parameters. Sliney et al. [13] investigated the friction and wear of an Al2O3-SiCw ceramic material sliding against Inconel 718 at a velocity of 0.5 m/s from 25 °C to 800 °C. Both the friction coefficient and wear of the ceramic decreased with increasing test temperature; the main wear mechanism was found to be fracture. DellaCorte [14] reported a similar wear mechanism in studying the high temperature tribological characteristics of Al2O3-SiCw at a sliding velocity of 2.7 m/s, though the wear rate was higher at high temperature than that at room temperature. As the temperature increased, SiC whiskers were more prone to being detached from the Al2O3 matrix, causing structural degradation of the ceramic and increasing wear volume. Deng [15] studied the friction and wear behavior of an Al2O3/TiB2/SiCw ceramic in sliding against cemented carbide (WC–Co) at 0.025 m/s and temperatures up to 800 °C. Once again, an increasing wear rate of the ceramic was reported with increasing test temperature. It was noticed in the literature that the effect of temperature on the tribological properties of alumina-based ceramics differed by changing the reinforcement material and sliding velocity.

The aim of this study is to study the tribological behavior of an alumina-based ceramic composite, toughened by 20 vol% SiCw and 4 vol% TiC nanoparticles (TiCn), in dry sliding against laser-heated (600 °C) and unheated nickel-based alloy (Inconel 718) at velocities up to 10 m/s. The objective achieved from the selection of test method and parameters was twofold: (i) to shed light on the wear mechanism of alumina-based ceramic tools in LAM, especially at high speeds, and (ii) to characterize the tribological properties of the novel alumina-based composite under consideration and compare it with a commercial alumina-based insert material. This work can provide guidance in applying alumina ceramic composite tools in dry or laser-assisted HSM of nickel-based alloys.

Section snippets

Materials and samples

A pin-on-disk setup was used to study the room-temperature and high-temperature sliding wear behavior of ceramic pins in unlubricated (i.e., dry) sliding against disks made of the nickel-based alloy Inconel 718. A novel alumina-based ceramic material (denoted hereinafter by AST) was hot-pressed at a temperature of 1700 °C under a pressure of 30 MPa for the duration of 30 min. The material, developed in a previous work [16], is composed of 20 vol% SiC whiskers (SiCw), 4 vol% TiC nanoparticles

Experimental and numerical results

The mean COF as function of sliding velocity for AST in both laser-heated and unheated tests is shown in Fig. 3. The mean COF in the two tests show very close values at the same sliding velocity. The trend shows decreasing COF with increasing sliding velocity from a value of 0.40 at 2.5 m/s to 0.19 at 10 m/s. The scatter in the COF data of both laser-heated and unheated tests decreases then slightly increases with increasing sliding velocity.

Fig. 4 shows the mean wear volume of AST as function

Discussion

The tribological characterization of AST (Al2O3-SiCw-TiCn) was conducted in unlubricated sliding contact against Inconel 718. At a same sliding velocity, the COF in both tests is similar, but the wear volume of AST in laser-heated tests was bigger than that in unheated tests; see Fig. 4.

Conclusions

The tribological behavior of a novel Al2O3-SiCw-TiCn ceramic composite (AST) in unlubricated sliding against laser-heated and unheated Inconel 718 was studied by pin-on-disk experiments. The wear mechanisms and the formation of tribochemical layers were analyzed and discussed. Finally, the wear behavior of AST was benchmarked against a reference Al2O3-SiCw composite (AS). The following points can be concluded:

  • In laser-heated and unheated tests both the COF and wear decrease with increasing

CRediT authorship contribution statement

Bin Zhao: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Funding acquisition, Writing - original draft. Iyas Khader: Conceptualization, Investigation, Methodology, Supervision, Writing - review & editing. Hanlian Liu: Funding acquisition, Resources. Tianfeng Zhou: Resources. Georg Konrath: Resources. Andreas Kailer: Funding acquisition, Project administration, Resources.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work has received funding from the National Natural Science Foundation of China [51675313], Beijing Institute of Technology Research Fund Program for Young Scholars [2020CX04252] and the Sino-German (CSC-DAAD) Postdoc Scholarship Program 2018 [57395819].

References (30)

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