Corrosion Behavior and Microstructure of Borided Tool Steel

Muzaffer Erdogan,Ibrahim Gunes

doi:10.1590/s1517-707620150002.0052

Abstract

In the present study, the corrosion behaviors of borides formed on cold work tool steel have been investigated in a 4% M HCl acid solution. Boriding was performed in a solid medium consisting of Ekabor-II powders at 850 and 950°C for 6 h. The boride layer was characterized by SEM, EDS, XRD and the hardness tester. XRD analysis of boride layers on the surface of the samples revealed the existence of FeB, Fe2B, CrB, Cr2B and MoB compounds. Depending on the chemical composition of substrates and boriding time, the boride layer thickness on the surface of the steel ranged from 13.14 μm and 120.82 μm. The hardness of the boride compounds formed on the surface of the samples ranged from 1806 to 2342 HV0,05, whereas Vickers hardness values of the untreated the samples was 428 HV0,05. The corrosion resistance of the borided steels was higher compared with that of the unborided steels. The borided steels increased the corrosion resistances of the steels 8-17- fold.

Highlights

Cold work tool steels have high chromium content and are commonly used engineering materials
The boriding process enhances the corrosion and wear resistance of metallic and non-metallic surfaces covered with boride layers [8,9]
Boride types formed on the surface of the cold work tool steel have a smooth morphology

Summary

Introduction

Cold work tool steels have high chromium content and are commonly used engineering materials. There has been extensive research on the development of surface treatment processes to improve the corrosion, wear and oxidation resistance of the cold work tool steels for high-temperature and high-pressure applications in recent years [1-7]. Boriding is a thermomechanical surface-hardening process, in which boron atoms are diffused into the surface of a workpiece to form borides with the base materials. The boriding process enhances the corrosion and wear resistance of metallic and non-metallic surfaces covered with boride layers [8,9]. Thermal diffusion treatments of boron compounds used to form iron borides typically require process temperatures of 700-1000 °C. The process can be carried out in solid, liquid, gaseous or plasma medium [10-13]

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