On the Prospects of Using Nanoindentation and Wear Test to Study the Mechanical Behavior of Fe-Based Metallic Glass Coat
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INTRODUCTION
FE-BASED metallic glasses indicate that it is a multicomponent alloy constituted of metal and metalloid elements.[1] This amorphous structure of metallic glasses gives them many unique properties compared to the crystalline materials and show the great candidates for the applications in aggressive environmental conditions including high wear and corrosion such as in ships, power stations, mines, and the machinery.[2–4] However, poor wear resistance in dry environments and very poor ductility significantly limit their range of possible applications in engineering and structural materials.[1,5,6] Furthermore, Fe-based bulk metallic glasses (BMG) always demonstrate no plastic deformation after yielding and no work hardening during the room temperature deformation due to the formation of highly localized shear bands.[7] It was found in the earlier study that Fe-based metallic glass coatings exhibited a very low-friction coefficient in a lubricating oil environment but a high-friction coefficient in a dry one. Therefore, such coatings were relatively poor in protecting against wear.[8] However, considerable efforts BEHROOZ MOVAHEDI is with the Department of Nanotechnology Engineering, Faculty of Advanced Sciences and Technologies, University of Isfahan, Isfahan 81746-73441, Iran. Contact e-mail: [email protected] Manuscript submitted August 22, 2016. Article published online January 5, 2017 1474—VOLUME 48A, MARCH 2017
have been devoted during the last decade to improve their plasticity by composition designing and developing BMG composites.[2,6] Interestingly, reinforcement of the secondary phases (particles or crystalline phase) in the glass matrix microstructure is one of the approaches to overcome these drawbacks.[8–10] The addition of fine second-phase particles such as WC, B4C, or TiN in BMG composites often improves wear resistance and mechanical properties because these particles effectively block the propagation of the shear bands.[11,12] Suh et al.[13] claimed that multi-wall carbon nanotubes with a high aspect ratio and a strong bonding character of the matrix have a great role in reinforcing the Fe-based composites. Terajima et al.[8] reported that the addition of 8 vol pct WC/12 wt pct Co to the Fe-Cr-Mo-C-B matrix increased the cross-sectional hardness from 6.47 to 8.53 GPa and reduced the friction coefficient from 0.65 to 0.5. These composite coatings showed an improved wear resistance by a factor of 2 to 5 as compared to the single-phase amorphous coating.[8,9,14,15] Boron carbide (B4C) with many unique properties, such as a high hardness (9.3 Mohs scale), high melting point 2723 K (2450 C), excellent thermal stability, remarkable chemical inertness, and high-abrasion resistance, is extremely appropriate for moderate and high temperature applications.[16] Yoon et al.[17] reported that the friction coefficient of Fe-based BMG/B4C composite coating (using nitrogen-shrouded plasma spraying system) was dependent on the fraction of B4C in the BMG METALLURGICAL AND MATERIALS TRANSACTIONS A
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