Microstructure and Properties of Cr-Fe2B Composite Coatings Prepared by Pack-Preboronizing Combined with Electro Brush-Plating

Jianjun Hu,Hongbin Xu,Hui Li,Yu Liu,Ning Guo,Yaoxin Pei,Xian Yang

doi:10.3390/coatings10060519

Jianjun Hu, Hongbin Xu + Show 5 more

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https://doi.org/10.3390/coatings10060519

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Abstract

Cr-Fe2B composite coatings were prepared on carbon steels by pack-boronizing followed by electro brush-plating. The microstructure and properties of the coatings annealed at different temperatures were studied. The coatings show a gradient structure composed of a Cr-layer and a Fe2B-layer and have excellent thermal stability, and no new layers and/or transition layers are formed in the coating during annealing up to 1000 °C. The Cr-layer has an amorphous structure and is transformed into nanosized grains when the annealing temperature increases to 700 °C. As the annealing temperature is further increased, the nanograins grow rapidly. The microcracks in the Cr-layer increase sharply after annealing at 550 °C and then decrease significantly with any further increase of the annealing temperature. The pre-deposited Fe2B-layer prevents the formation of carbon-poor zones in the steel substrate during annealing. It is considered that high-temperature (>700 °C) annealing helps to eliminate coating defects, increase the coating density and obtain better wear resistance and corrosion resistance. Surprisingly, the as-plated and low temperature annealed samples also show good wear resistance and corrosion resistance, which may be related to their amorphous structure and nanocrystalline structure.

Highlights

As an important part of power transmission and speed regulation, the performance of the entire equipment is affected by gears [1,2,3]
Cr-Fe2B composite coating was deposited on the surface of the AISI 5140 steel by pack-boronizing followed by electro brush-plating
The microstructure and properties of the coating annealed at different temperatures were investigated

Summary

Introduction

As an important part of power transmission and speed regulation, the performance of the entire equipment is affected by gears [1,2,3]. When a gear is used in a complex environment such as high speed, high temperature, and/or high corrosion, the gear surface is required to have multiple functional characteristics such as high hardness, good wear resistance and good corrosion resistance

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Conclusion