Novel utilization of powder-suspension hybrid feedstock in HVAF spraying to deposit improved wear and corrosion resistant coatings

Satyapal Mahade,Lidia Baiamonte,Esmaeil Sadeghimeresht,Shrikant Joshi,Francesco Marra,Stefan Björklund

doi:10.1016/j.surfcoat.2021.127015

Satyapal Mahade, Lidia Baiamonte + Show 4 more

Open Access

https://doi.org/10.1016/j.surfcoat.2021.127015

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Abstract

Deployment of a suspension feedstock has been known to alleviate problems associated with using sub-micron and nanosized powder feedstock for thermal spraying of monolithic as well as powder-suspension ‘hybrid’ composite coatings. However, a powder-suspension hybrid feedstock has never been previously used in high-velocity air-fuel (HVAF) spraying. In this work, for the very first time, a chromium carbide (Cr3C2) suspension has been co-sprayed along with an Inconel-625 (IN-625) powder by the HVAF process as an illustrative case study. Two variants of the IN-625 + Cr3C2 hybrid coatings were produced by varying relative powder-suspension feed rates. For comparison, pure IN-625 coating was also deposited utilizing identical spray parameters. Detailed microstructural characterization, porosity content, hardness measurement and phase analysis of the as-deposited coatings was performed. The suspension-derived carbides were retained in the bulk of the coating, resulting in higher hardness. In the dry sliding wear test, the hybrid coatings demonstrated lower wear rate and higher coefficient of friction (CoF) compared to the conventional, powder-derived IN-625 coatings. Furthermore, the wear rate improved slightly with an increase in Cr3C2 content in the hybrid coating. Post-wear analysis of the worn coating, worn alumina ball and the wear debris was performed to understand the wear mechanisms and material transfer in the investigated coatings. In the potentiodynamic polarization test, higher corrosion resistance for hybrid coatings than conventional IN-625 coatings was achieved, indicating that the incorporation of a secondary, carbide phase in the IN-625 matrix did not compromise its corrosion performance. This work demonstrates a novel approach to incorporate any finely distributed second phase in HVAF sprayed coatings to enhance their performance when exposed to harsh environments.

Highlights

Protective coatings are utilized in vast majority of applications to enhance the performance and durability of engineering components
Thermal spray route such as High Velocity Air Fuel (HVAF) involves lower processing temperature than plasma spray and high velocity oxy-fuel (HVOF) processes, which is beneficial in depositing temperature-sensitive carbide-based materials [1,2]
This work demonstrated the possibility of utilizing a powder-suspension hybrid feedstock for HVAF spraying

Summary

Introduction

Protective coatings are utilized in vast majority of applications to enhance the performance and durability of engineering components. Adequate thermal and kinetic energy is imparted to the feedstock, which eventually deposits as a splat onto the substrate Thermal spray route such as High Velocity Air Fuel (HVAF) involves lower processing temperature than plasma spray and high velocity oxy-fuel (HVOF) processes, which is beneficial in depositing temperature-sensitive carbide-based materials [1,2]. All the above thermal spray processes have limitations in processing submicron and nano-sized feedstock due to problems associated with their feeding [1,3]. Liquid feedstock utilizing such fine-sized powder suspended in solvents like water or ethanol overcomes the above challenges [4,5]. Never previously attempted, such hybrid spraying could be an interesting approach to explore in an HVAF and constitutes the main focus of this study

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