Effect of Deep Cryogenic Treatment on Corrosion Properties of Various High-Speed Steels

Jure Voglar,Patricia Jovičević-Klug,Bojan Podgornik,Živa Novak,Tadeja Kosec

doi:10.3390/met11010014

Abstract

The aim of the study was to evaluate the corrosion properties of three different grades of high-speed steel following a heat treatment procedure involving deep cryogenic treatment after quenching and to investigate how these properties are connected to the microstructure and hardness of the material. The hardness of steels was measured, and microstructural properties were determined through observation of the metallographically prepared steels using scanning electron microscopy. These studies were complemented corrosion evaluation by the use of corrosion potential measurement and linear polarization measurement of steels in a sodium tetraborate buffer at pH 10. The results showed that the deep cryogenic procedure of high-speed steel changed the microstructure and consequently affected the hardness of the investigated steels to different extents, depending on their chemical composition. Corrosion studies have confirmed that some high-speed steels have improved corrosion properties after deep cryogenic treatment. The most important improvement in corrosion resistance was observed for deep cryogenically treated high-speed steel EN 1.3395 (M3:2) by 31% when hardened to high hardness values and by 116% under lower hardness conditions. The test procedure for differentiating corrosion properties of differently heat-treated tool steels was established alongside the investigation.

Highlights

Tool steels are used in many industrial manufacturing processes, including machining, cutting, stamping, pressing, forging, and others [1]
The results showed that the deep cryogenic procedure of high-speed steel changed the microstructure and affected the hardness of the investigated steels to different extents, depending on their chemical composition
As a consequence of the different austenitization temperature, the crystal grains of the samples quenched from the upper austenitization temperature (1230 ◦C; A1 and A2) were slightly larger than the crystal grains of the samples austenitized at a lower temperature (1180 ◦C; A3 and A4), which were between 10 μm and 25 μm

Summary

Introduction

Tool steels are used in many industrial manufacturing processes, including machining, cutting, stamping, pressing, forging, and others [1]. During their lifetime, the tools (e.g., drills) are subject to demanding operating conditions such as high stresses, high temperatures, and their fluctuations. The wear behavior and lifetime of the tools are affected by the properties of the tool steels [1]. The desired properties of tool steels are high hardness at both low and high temperatures, high compressive strength, fatigue strength, toughness at operational temperatures, wear resistance, thermal fatigue resistance, and corrosion resistance [1]. Tool steel properties depend on their chemical composition and heat treatment procedure, both of which affect their microstructure

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Conclusion