Presentation Title

Twin wire-arc spraying of steel coatings

Faculty Mentor

Nicole Wagner

Start Date

17-11-2018 9:30 AM

End Date

17-11-2018 9:45 AM

Location

C304

Session

Oral 2

Type of Presentation

Oral Talk

Subject Area

engineering_computer_science

Abstract

Abstract

Twin wire-arc spraying has existed for almost a century, but not until the past couple decades has it become a relevant surface coating process. This thermal spraying technique, uses an electric arc to melt metallic wires. The molten droplets that are created are propelled by the high velocity carrier gas and impinge onto a substrate. The process has been used to fabricate industrial coatings or to fill cracks that have developed in a part. It is the desire to expand the applications and areas in which this spraying technique can be implemented. A way of achieving this is by understanding how the process conditions of twin wire-arc spraying affect the coating morphology and composition of the base and spray material. In this research, an Oerlikon Metco FlexiArc 300 twin-wire arc plasma spraying system was used with 1.6mm diameter steel wires to create coatings on carbon steel substrates. Process conditions, including power, standoff distance, and coating thickness were varied. The coating morphology was evaluated with scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) was used to investigate the coating composition. Distinct light and dark regions were observed throughout the coating with variations in the composition of iron and oxygen between the regions. The morphology seen in SEM images indicated cracking throughout the laminae structures. In addition, coatings appeared delaminated from their substrates, with minimal adhesion. Both cracks and delamination of the coatings suggest stress build-up in the coating generated by the process.

Summary of research results to be presented

A twin-wire arc plasma spraying process was used to create steel coatings on steel substrates. Three coatings were evaluated with varying power and deposition time. Deposition rates varied for different power settings. The coatings were analyzed using scanning electron microscopy (SEM). The morphology seen in SEM images indicated cracking throughout the laminae structures. In addition, coatings appeared delaminated from their substrates, with minimal adhesion. Both cracks and delamination of the coatings indicated stress build-up in the coating generated by the quenching process. Since the substrates were at room temperature prior to starting the spraying process, molten spray particles were immediately quenched at the substrate surface.

Elemental analysis from energy dispersive x-ray spectroscopy (EDS) showed segregation, indicated by light and dark regions that existed throughout the samples. These regions had varying iron-to-oxygen ratios. The lighter regions, those with heavier elements, had greater than 90% iron with 2-4% oxygen. These lighter areas had either pores or no observable pores present. Darker regions, those with lighter elements, ranged from 70-80% iron with 20-30% oxygen. These regions had more cracks and larger voids. These cracks were seen to terminate or run along the borders with the lighter regions.

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Nov 17th, 9:30 AM Nov 17th, 9:45 AM

Twin wire-arc spraying of steel coatings

C304

Abstract

Twin wire-arc spraying has existed for almost a century, but not until the past couple decades has it become a relevant surface coating process. This thermal spraying technique, uses an electric arc to melt metallic wires. The molten droplets that are created are propelled by the high velocity carrier gas and impinge onto a substrate. The process has been used to fabricate industrial coatings or to fill cracks that have developed in a part. It is the desire to expand the applications and areas in which this spraying technique can be implemented. A way of achieving this is by understanding how the process conditions of twin wire-arc spraying affect the coating morphology and composition of the base and spray material. In this research, an Oerlikon Metco FlexiArc 300 twin-wire arc plasma spraying system was used with 1.6mm diameter steel wires to create coatings on carbon steel substrates. Process conditions, including power, standoff distance, and coating thickness were varied. The coating morphology was evaluated with scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) was used to investigate the coating composition. Distinct light and dark regions were observed throughout the coating with variations in the composition of iron and oxygen between the regions. The morphology seen in SEM images indicated cracking throughout the laminae structures. In addition, coatings appeared delaminated from their substrates, with minimal adhesion. Both cracks and delamination of the coatings suggest stress build-up in the coating generated by the process.