Microstructure, Microhardness, and Wear Properties of Cobalt Alloy Electrodes Coated with TiO2 Nanoparticles

Sebastian Balos,Petar Janjatovic,Branka Pilic,Miroslav Dramicanin,Pavel Hanus,Lucyna Jaworska,Danka Labus Zlatanovic

doi:10.3390/met9111186

Abstract

In this paper, the influence of TiO2 nanoparticle coating on cobalt-based electrodes was studied. Different coating treatment times were applied, and the results were compared to the hard-faced layer obtained with unmodified electrodes. The hard facing was done in three layers, the first being a Ni-based interlayer, followed by two layers of corrosion and wear-resistant Co-based Stellite 6 alloy. Pin-on-disc wear testing was applied, along with the metallographic study and hardness measurements of the hard-faced layers. Furthermore, energy-dispersive X-ray spectroscopy (EDS) analysis was conducted. It was found that the microstructural properties, as well as microhardness profiles, are modified in hard-faced layers obtained with modified electrodes. Interdendritic distances are altered, as are the dendrite growth directions. Titanium oxides are formed, which, along with the present complex carbides, increase the wear resistance of the hard-faced layers compared to layers obtained with untreated electrodes.

Highlights

Cobalt-based alloys, commonly known as Stellites, are well-known wear and corrosion resisting alloys [1]
The aim of this study is to explore the influence of nanoparticles introduced on the Co-based hard-facing electrode with different immersion times on the wear resistance of the resulting hard-faced layer
Based on the results shown in this work, the following conclusions can be drawn:

Summary

Introduction

Cobalt-based alloys, commonly known as Stellites, are well-known wear and corrosion resisting alloys [1]. Stellites are Co-Cr-W-C alloys, containing around 30% chromium and 4% to 14% tungsten, while some alloys have their tungsten replaced with molybdenum for increased resistance to reductive media. They contain up to around 2.5% of carbon, to form wear-resisting complex carbides [2,3,4,5]. Stellite alloys properties are the result of the combined effects of the relatively ductile Co-based matrix that supports relatively hard carbides, providing wear resistance at both room and elevated temperatures up to 600 ◦ C [6,7].

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