Droplet assisted laser micromachining of hard ceramics

José Manuel López López,Alan Bakrania,Jeremy Coupland,Sundar Marimuthu

doi:10.1016/j.jeurceramsoc.2016.04.021

José Manuel López López, Alan Bakrania + Show 2 more

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https://doi.org/10.1016/j.jeurceramsoc.2016.04.021

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Abstract

Hard ceramic materials like tungsten carbide (WC) are extensively used in high value manufacturing, and micromachining of these materials with sufficient quality is essential to exploit its full potential. A new micro-machining technique called droplet assisted laser micromachining (DALM) was proposed and demonstrated as an alternative to the existing nanosecond (ns) dry pulse laser ablation (PLA). DALM involves injecting liquid micro-droplets at specific frequency during the nanosecond laser micromachining to create impulse shock pressure inside the laser irradiation zone. The impulse shock pressure is generated due to the explosive vaporisation of the droplet, during its interaction with high temperature laser irradiation zone. In this paper, the DALM uses a nanosecond pulsed Nd:YAG laser to machine tungsten carbide substrate. The results suggest that the impulse shock pressure generated during the DALM process can transform the melt ejection mechanism of the ns laser micromachining process. The change in ejection mechanism results in a 75% increase in material removal rate and 71% reduction in the spatter redeposited compared to conventional dry ns laser micromachining.

Highlights

Hard, advanced ceramic materials such as tungsten carbide (WC) have excellent mechanical and thermal properties, including hardness, wear resistance and retention of strength at elevated temperatures, making them suitable for a wide range of applications from aerospace to tooling
The ablation trend of droplet assisted laser micromachining (DALM) based laser micromachining is similar to the one observed with dry pulse laser ablation (PLA) process, the magnitude of removal rate is significantly higher in DALM based process [4,6,11]
Compared to dry PLA process, the DALM process can result in around 75% increase in material removal rate

Summary

Introduction

Hard, advanced ceramic materials such as tungsten carbide (WC) have excellent mechanical and thermal properties, including hardness, wear resistance and retention of strength at elevated temperatures, making them suitable for a wide range of applications from aerospace to tooling. It is these properties that make micromachining of WC challenging by conventional means and machining these materials is essential to fully realise their potential. Micromachining using short (microsecond-nanosecond) and ultra-short (picosecond-femtosecond) pulsed lasers is becoming an important process to machine hard materials like WC.

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