Collaboration with TWI on Core Research Programme in selective laser melting

A new TWI Members’ Core Research Programme (CRP) has been set up in collaboration with HBM Prenscia. The TWI CRP aims to provide a comprehensive evaluation of fatigue performance enhancement through elimination of porosity in additively manufactured (AM) material by Selective Laser Melting (SLM).

Industrial need

With its greater design freedom for complex shaped components and its higher buy-to-fly ratio with minimal material waste compared with conventional manufacturing, SLM of metallic alloys is of significant interest for a number of industrial applications. However, there is a lack of mechanical properties design data for AM materials to give designers confidence in designing and using SLM parts. Currently, companies use single part qualification, resulting in very conservative ‘design allowables’ and high costs associated with single part qualification. Equally, component quality is sensitive to a number of factors, including both the SLM system set up and processing parameters related to specific alloy systems. These parameters significantly affect resultant defect populations in the microstructures of the as-SLM processed material, which determine the subsequent as-built mechanical properties. In particular, fatigue performance, which is dictated by the size, morphology and volume fraction of the defects present. Whilst tensile properties are commonly examined, there is much less data available on fatigue performance, and where available is often limited to a small number of test samples per condition in low cycle fatigue.

SLM additive manufacturing at the TWI Technology Centre - Yorkshire
SLM additive manufacturing at the TWI Technology Centre - Yorkshire

Concept

This project differs from a conventional TWI CRP because the size and scope of the programme will be considerably extended to leverage additional resources, provided in-kind from HBM Prenscia. Coupled with TWI’s expert processing knowledge of SLM, the Advanced Materials Characterization & Test facility (AMCT) will generate statistically significant fatigue performance data on a selection of industrially relevant materials (Ti6Al4V, In718, AlSi10Mg). Additionally, this project aims to quantify the effects of post processing (HIP vs. non-HIP) variations in raw material production, powder sourcing, handling and recycling of powders in SLM. Thus, enabling TWI Members to make evidence-based decisions in the design, modelling and development of new applications for SLM components, and add new strain-life fatigue materials data for the nCode Premium Materials Database.

Key deliverables of the TWI CRP

A proven methodology for the derivation of optimised SLM process parameters with definitive fatigue performance data to demonstrate and support this.
Statistically significant data sets benchmarking fatigue performance of a range of materials (Ti6Al4V, In718, AlSi10Mg,) produced by optimised SLM processing.
A set of guidelines addressing SLM powder sourcing, handling and recycling, and how these can be implemented.
SLM additive manufacturing at the TWI Technology Centre - Yorkshire
Strain-controlled fatigue testing at the HBM Prenscia “Advanced Materials Characterization & Test” facility