Mechanical properties and tribological behavior of Fe/nano-diamond composite prepared by hot-press sintering

https://doi.org/10.1016/j.ijrmhm.2020.105412Get rights and content

Highlights

  • A microstructure of pearlite was formed in the sintered Fe/ND composites.

  • Fe/ND composites exhibit higher hardness, compressive strength, and flexural strength than sintered Fe.

  • Fe/ND composite with higher content of ND produce lower friction coefficient (COF) and higher wear resistance.

Abstract

In the present study, Fe matrix composites reinforced with nano-diamond (ND) particulates were fabricated by hot-press sintering. The influence of the concentration of ND on the mechanical and tribological properties of as-sintered Fe/ND composites was investigated. The microstructures and properties of the Fe/ND composites were examined using X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. A pearlite microstructure is formed due to the reaction between Fe and ND in the sintering. The presence of ND provides higher hardness, compressive strength, and flexural strength. The composite with 1 wt% ND exhibits 51.5% higher hardness, 37.4% higher compressive strength, and 76.2% higher flexural strength than sintered Fe. In addition, the wear resistance will increase as the ND concentration increases. Fe/2 wt% ND composite exhibits much lower friction coefficient (COF) and higher wear resistance than a Fe/1 wt% ND composite and sintered Fe.

Introduction

Particulate-reinforced Fe matrix composites are widely used in different fields due to their high hardness, strength, wear resistance, and temperature resistance [1,2]. Particles with high hardness and Young's modulus such as Al2O3, ZrO2, TiN, Si3N4, SiC, and TiC are commonly used as reinforcements in Fe matrix composites [[3], [4], [5], [6], [7], [8]]. Numerous methods for preparing particle-reinforced Fe matrix composites, such as powder metallurgy (PM) [9], laser cladding [10], solid-phase diffusion [11], and cast sintering [12] have been reported. PM is most commonly used for its low processing cost [13].

Among particles with high hardness and Young's modulus, nano-diamond (ND) exhibits great potential for tailoring the mechanical properties and tribological behavior of various composite matrices [14]. ND possesses many superior properties of bulk diamond, including its chemical stability, high thermal conductivity, and high hardness [15,16]. Its unique properties make ND a promising candidate for use as a reinforcement material [[17], [18], [19], [20]], especially for metal matrix composites (MMCs) formed from Al [21], Ni [22], Cu [23], Alsingle bondMg [24], Ti [25], Alsingle bondCu [26], and Nisingle bondFe alloy [15]. The Al-ND coatings were fabricated by the flame spraying route, yielding a coating with 5.7-fold higher wear resistance compared with the Al coating [27]. In another study, Zhang et al. [28] found that a Ti/0.5 wt% ND composite exhibits 60.2% higher hardness, 27.3% higher Young's modulus, and 12% higher yield strength (σ0.2) than Ti. Additionally, the dependence of mechanical properties and strengthening mechanisms on ND size (0.005, 0.1, 0.2, and 3 μm) in Ti-MMCs were investigated, and it was found that Ti/ND has a desirable combination of strength, ductility, and wear resistance [29,30]. The ND reinforcement effect can be attributed to the grain refinement strengthening, Orowan strengthening, load transfer strengthening and coefficients of thermal expansion (CTE) mismatch strengthening [[29], [30], [31]]. Interfacial bonding between Fe and ND has been theoretically investigated [32]. However, the effects of ND on the mechanical properties and microstructure of Fe matrix composites have rarely been investigated. In the present study, the Fe/ND composites were prepared by hot-press sintering. The effect of ND content on the microstructure, mechanical properties, and tribological behavior of the composites was investigated.

Section snippets

Experimental procedure

The details of commercially obtained raw powders are listed in Table 1. ND powders were dispersed in an alcohol solution with added stearic acid. Fe powders with different mass fractions (0, 1, and 2 wt%) of ND powder were mixed with the stearic acid solution and milled with a planetary ball mill for 10 h (250 rpm, 8:1 ball to powder ratio). The mixture was dried in air at 70 °C for 2 min and then unidirectionally pressed into a cylinder with 30 mm diameter and 8 mm height at 150 MPa. The green

Thermal behavior of Fe/ND composite material during heating

A DSC curve gathered from the Fe/2 wt% ND composite is shown in Fig. 1. There is an endothermic peak centered at 772 °C, and one exothermic peak centered at 906 °C. The endothermic peak centered at 772 °C is due to a phase transformation from α-Fe to γ-Fe [2]. An exothermic peak centered at 906 °C is associated with formation of carbides (transformation from austenite to Fe3C), which is consistent with the phase diagram for an Fesingle bondC system. This means there is a reaction between ND and Fe above

Conclusions

The microstructure of pearlite was formed in hot-press sintering of Fe/ND composites.

Fe/ND composites exhibit higher hardness, compressive strength, and flexural strength than sintered Fe. The composite with 1 wt% ND exhibits 51.5% higher hardness, 37.4% higher compressive strength, and 76.2% higher flexural strength than sintered Fe.

The wear resistance will increase as the ND concentration increases. The Fe/2 wt% ND composite exhibits much lower friction coefficient (COF) and higher wear

Declaration of Competing Interest

We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work. There is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled.

Acknowledgements

The authors acknowledge financial support from the National Natural Science Foundation of China (NSFC, Grant No. 51775118, 51965005), the Natural Science Foundation of Guangxi (Grant No. 2018GXNSFAA281258), the Guangzhou Foreign Science and Technology Special Cooperation Project (Grant No. 201907010022), Foshan Core Technical Project (Grant No. 1920001000361), Guangxi Key Laboratory of Superhard Materials (China Nonferrous Metal Guilin Research Institute of Geology for Mineral Resources) (No.

References (36)

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