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PTA Overlays - A High Performance Armature

Peter Cameron
4th February 2009

Introduction

This high speed, heavy duty armature arrived at our workshop with a 0.25mm bend in it from the bearing position to the end of the shaft. A centre was re-cut, the shaft was pre-turned by 0.5mm per side so that final machining avoided the PTA (Plasma Transferred Arc) overlay interface.

Process

An overlay of a nickel, chrome, silicon and boron was selected for its hardness and corrosion resistance. A 2mm thick overlay was applied at very low heat input to minimize the risk of any distortion and keep the heat affected zone to a bear minimum. After slow cooling in a heat blanket the PTA overlay was then finish machined and returned to the customer within 3 working days!


Armature has been overlaid to remove a bend in the shaft

PTA overlay was then finish machined

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