On the use of multiple layer thicknesses within laser powder bed fusion and the effect on mechanical properties

Abstract

Laser Powder Bed fusion is capable of rapid production of parts, from conception, compared with traditional manufacturing methods. This said, the time taken to fabricate a single part can still be significant – typically many hours. Processing thicker layers, and hence fewer total layers, in the Laser Powder Bed Fusion process, is an effective way to reduce build times. However, mechanical performance can suffer as a result of this strategy. This study proposes and demonstrates a method to enable the interlacing of multiple layer thicknesses within one part, allowing for finer layers within regions where they are specifically required, whilst maintaining overall component integrity for specific load cases. Thicker layers are used within regions with lower property requirements in order to optimise an overall part for improved production rate. The design of interfaces between two disparate layer thickness regions could also be tailored for control of material properties and such will be investigated in an independent study. Ti6Al4V LPBF samples are fabricated, characterised by way of tensile testing, porosity analysis and microstructural analysis. The study demonstrate parts can be additively built using multiple layer thickness regions with consistent ultimate tensile strength (1110–1135 MPa) and varying penalties to ductility, depending on layer thickness and interface design (elongation to failure reductions up to 40% in the most extreme case).