In-situ synthesized novel eyeball-like Al2O3/TiC composite ceramics reinforced Fe-based alloy coating produced by laser cladding

https://doi.org/10.1016/j.surfcoat.2020.125671Get rights and content

Highlights

  • New type laser cladding material system is designed with Fe60 alloy and Ti3SiC2.

  • A novel “eyeball” structure is formed in the cladded coating.

  • Ti3SiC2 can improve the wear and corrosion resistance of the cladded coating.

Abstract

In this study, the precursor mixtures of Fe-Cr-C-B alloy powders and 0, 10 and 20 wt% Ti3SiC2 is successfully cladded on 16Mn steel substrate by laser cladding (LC). Microstructure and properties of composite coatings are explored by using X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectra (XPS), electrochemical workstation, Vickers hardness tester and UMT-2 tribo-meter. Results show that the phases in the composite coating with Ti3SiC2 addition mainly are super saturated solid solution α-Fe, hard phases such as eyeball-like Al2O3/TiC composite ceramics, Ti(B,C)2, TiC, Fe3C, γ-(Fe, Ni)/(Cr, Fe)23C6 laminar eutectics and Ti3SiC2 etc. The microhardness, wear and corrosion resistance of composite coatings increase with the weight percent of Ti3SiC2 increasing from 0 to 20%. The existence of super saturated solid solution α-Fe, hard phases such as Al2O3/TiC composite ceramics, Ti(B,C)2, TiC and Fe3C etc. and the Ti3SiC2 solid lubricant contribute to the higher microhardness and wear resistance. The increased corrosion resistance of coatings is attributed to the fact that Cr is the important element which increases the corrosion resistance of the composite coating. With Ti3SiC2 addition increasing, more Ti atoms are easy to interact with C atoms to form TiC carbides, which remain higher content of free Cr atoms in composite coatings.

Introduction

In recent decades, LC which can melt rapidly metal surface and then solidify with a high cooling rate has been an advanced and efficient method for metal surface modification [[1], [2], [3], [4], [5]]. Owing to key disadvantages of low hardness, weak corrosion and wear resistance, traditional steels are unable to be suitable for their application under harsh working environment. LC produces hard protective coatings, which can be independent of the substrate. According to some former reports, coatings fabricated by LC have high hardness, good corrosion or wear resistance, which is mainly enhanced by hard phases, either directly introduced or in-situ formed, such as ZrB2, TiC, TaC, Tisingle bondSi compounds and carbon fibers (CFs) etc. For instance, Guo et al. [6] successfully fabricated ZrB2 reinforced Ni-based alloy coatings on the surface of titanium substrate, and ZrB2 effectively increased the wear resistance of the substrate by approximately 4 times. Wu and Hong [7] found that TiCp reinforced Ni-based alloy coatings consisting of original TiCp and in-situ precipitated TiCp showed the higher wear resistance. Yu et al. [8] investigated that the hardness and wear resistance of LC Ni-based coating with Ta addition. Results showed that fine TaC hard particles were synthesized in the composite coating, which significantly improved the coating's hardness and wear resistance. Wu et al. [9] reported that Tisingle bondSi compounds contributed to the increase of corrosion potential (Ecorr) and the decrease of corrosion current density (Icorr), increasing the corrosion resistance of the clad coating. Lei et al. [10] reported that CFs are added to Ni-based coatings, and the corrosion and wear resistances of Ni-based coatings are effectively improved. Shi et al. [11] also found that CFs have high temperature oxidation resistance and good corrosion resistance, significantly enhancing the mechanical properties of composites. Zhao and Zhou et al. [12] fabricated the Cu88Fe12 immiscible coating by laser cladding, and found that a large amount of Fe-rich particles distributed homogeneously in the ε-Cu matrix, which led to the higher hardness and wear resistance of the immiscible coating comparing with brass.

It is reported that an attention has been increasingly paid to LC ceramics reinforced metal matrix coating in the past few years, and it becomes one of the popular issues in the area of metal surface modification. However, ceramics are easily peeled off from the matrix under cyclic stress, which is detrimental to the anti-wear capability of composite coatings. Therefore, to solve the problem of severe spalling, the composite ceramics is used as a reinforcement to enhance the composite coating. It is because the composite ceramics can largely prevent the reinforcements being ripped out from the matrix during the wear process and is beneficial to the wear resistance [13]. As a result, researches on the composite ceramics reinforced coatings are of practicality, which will become a hot trend in industrial applications.

In this paper, our group successfully fabricates the Al2O3/TiC composite ceramics reinforced composite coatings by LC the precursor mixture of Fe-based alloy powders and Ti3SiC2, and its microstructure, microhardness, corrosion and wear resistances are investigated in detail. This provides a good reference for domestic and foreign scholars in terms of fabricating other composite ceramics reinforced composite coatings.

Section snippets

Preparation of the composite coatings

16Mn steel, dimensions of 100 m × 40 mm × 8 mm, was adopted for the substrate with the nominal chemical composition (wt%) of Mn (1.2–1.6), Ni (≤0.3), Cr (≤0.3), C (0.1–0.2), Cu (≤0.25), S (≤0.03), Si (0.2–0.6), P (≤0.03), and Fe (bal.). Fe60 alloy powders and Ti3SiC2 particles were well-mixed in planetary ball mill for the preparation of coating materials, in which the weight percent of Ti3SiC2 particles was 10% and 20%, respectively. Fe60 alloy powders with the alloy elements (wt%): Ni (0.3),

Macroscopic feature and microstructure

Fig. 2, Fig. 3 show the surface macro morphology and cross-section profiles of composite coatings, respectively. Composite coatings exhibit smooth and continuous uniform surfaces, and the cross-section are free of any defects such as holes and cracks. Moreover, as shown in Fig. 3(d–f), upper regions of the bonding line show a combination of the planar and cellular crystals. According to the corresponding linear analysis (Fig. 4), melted alloy atoms between cladded coatings and the substrate

Conclusion

In the present work, Fe-based composite coatings with Ti3SiC2 addition are successfully fabricated by LC. It is found that the composite coatings have high quality metallurgical bonding to the steel substrate, and there hardly exists any defects. The bottom, middle and upper zones of the composite coating show different microstructure characteristics. The main conclusions are drawn as follows.

  • (1)

    Three phases are in-situ formed in the composite coatings. The first one is Al2O3/TiC composite

CRediT authorship contribution statement

Zhencai Zhu:Conceptualization, Methodology, Software, Formal analysis, Investigation, Data curation.Jianfeng Li:Conceptualization, Methodology, Software, Formal analysis, Investigation, Writing - review & editing.Yuxing Peng:Supervision.Gang Shen:Supervision.

Declaration of competing interest

The authors declare no conflict of interest.

Acknowledgements

The authors would like to express their gratitude for financial support from the Key Project of National Natural Science Foundation of China (U1510205).

References (35)

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