Abstract

To improve the wear resistance of type 45 steel surfaces, Ni–Mn alloy coatings are prepared through electrodeposition under different sodium citrate concentrations based on which SiC particles of varying concentrations are added to prepare Ni–Mn–SiC composite coatings. The coatings are characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, microhardness testing, surface roughness meter, composite material surface performance testing, and laser scanning confocal microscopy. The results show that adding an appropriate concentration of sodium citrate into the electrolyte can significantly improve the Mn content in the coatings; however, an excessively high concentration increases the residual stress of the coatings and induces cracks on the surface. When the sodium citrate concentration is 40 g/L, the microhardness and wear resistance of the coatings are optimum. The average microhardness of the Ni–Mn alloy coatings is 522.8 HV0.05, and the minimum scratch area of the wear mark is 9526.26 μm2. The addition of SiC particles improves the surface integrity of the composite coatings and further improves the microhardness and wear resistance of the coatings. The composite coating has a maximum average microhardness value of 648.7 HV0.05 for SiC particle concentration of 4 g/L; this value is nearly 25% higher than that of pure Ni–Mn alloy coatings; the minimum scratch area of the wear mark is reduced to 7160.46 μm2.

Highlights

  • In recent years, with the development of aviation, aerospace, electronics, and transportation industries, higher requirements are placed on the strength, hardness, and wear resistance of engineering materials

  • This paper explored the effects of sodium citrate concentration on the surface and cross-sectional morphology, composition, phase structure and wear resistance of the Ni–Mn alloy coatings, based on which different concentrations of

  • We explored the effect of SiC particle concentration on the Ni–Mn–SiC composite coatings

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Summary

Introduction

With the development of aviation, aerospace, electronics, and transportation industries, higher requirements are placed on the strength, hardness, and wear resistance of engineering materials. An insufficient surface protection performance of metal parts decreases the overall service life of mechanical products. Electrodeposition is a common way to prepare composite coatings that can protect material surfaces and help repair worn surfaces; this method is cost effective and has an excellent performance [3,4,5]. A pure Ni substrate has been widely studied and applied owing to its good mechanical properties and chemical stability. Adding transition metal elements to pure Ni coatings, such as Mn, can help form Ni–Mn alloy coatings and improve the surface morphology and mechanical and chemical properties of coatings [13,14,15]. Wang and Zhang [16] found that electrodeposited

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