Using wire shaping techniques and holographic optics to optimize deposition characteristics in wire-based laser cladding.

N J Goffin,R L Higginson,J R Tyrer

doi:10.1098/rspa.2016.0603

Abstract

In laser cladding, the potential benefits of wire feeding are considerable. Typical problems with the use of powder, such as gas entrapment, sub-100% material density and low deposition rate are all avoided with the use of wire. However, the use of a powder-based source material is the industry standard, with wire-based deposition generally regarded as an academic curiosity. This is because, although wire-based methods have been shown to be capable of superior quality results, the wire-based process is more difficult to control. In this work, the potential for wire shaping techniques, combined with existing holographic optical element knowledge, is investigated in order to further improve the processing characteristics. Experiments with pre-placed wire showed the ability of shaped wire to provide uniformity of wire melting compared with standard round wire, giving reduced power density requirements and superior control of clad track dilution. When feeding with flat wire, the resulting clad tracks showed a greater level of quality consistency and became less sensitive to alterations in processing conditions. In addition, a 22% increase in deposition rate was achieved. Stacking of multiple layers demonstrated the ability to create fully dense, three-dimensional structures, with directional metallurgical grain growth and uniform chemical structure.

Highlights

Laser cladding is the term used to describe the use of a laser to coat the surface of one material with a different material, in order to alter the surface properties
The majority of commercial efforts have been focused on powder-based laser cladding, with powder-fed systems such as LENSTM and direct metal deposition (DMD) [1]; some research has been conducted into the use of wire as a source material
— The cross-sectional shape of pre-placed flat wire is better suited to substrate wetting than round wire, primarily due to the fact that the flat wire–substrate interface extends across the whole wire width whereas the round wire contacts the substrate only in the centre

Summary

Introduction

Laser cladding is the term used to describe the use of a laser to coat the surface of one material with a different material, in order to alter the surface properties. Williams et al [8] demonstrated the ability to use a metal inert gas (MIG)-based system to create high-quality large components, including unsupported overhanging structures This process is a ‘near-net shape’ manufacturing process, requiring post machining for a completed structure. Royce experimented with this technique in order to maximize heat absorption, as detailed in their patent EP 1454703 B1 [11] This proposes the use of preheated rollers to alter the cross-sectional shape of the wire just prior to processing, easing the reshaping of the wire and reducing the work hardening effect. Other research by Fux & Luft [12] investigated the creation and use of amorphous metal ribbons for laser deposition, using a rapidly scanned laser to cover the whole width of the ribbon This was not wire in the traditional sense but was successful in creating low-dilution clad tracks. These results are developed with the demonstration and characterization of multilayer stacking using shaped wire

Material and methods

Pre-placed experimental comparison between round and flat wire

Nd:YAG laser wire-fed deposition

Findings

Discussion

Conclusion