Isostatic pressing assisted indirect selective laser sintering of alumina components

Purpose The purpose of this paper is to assess a new powder metallurgy process to make alumina parts through indirect selective laser sintering (SLS). Density measurements, some geometrical assessments and scanning electron microscopy (SEM) microstructural analyses are performed after each stage of the process, allowing an objective overview to be provided of the challenges and possibilities for the processing of high density technical ceramic parts through SLS of ball milled alumina/polyamide powder agglomerates. Design/methodology/approach The powder production by ball milling, SLS, cold isostatic pressing (CIP) or quasi isostatic pressing (QIP), debinding and sintering (FS) stages of the powder metallurgy process were sequentially investigated. Findings Alumina parts with a density up to 94.1 per cent could be produced by a powder metallurgy process containing an SLS step. Microstructural investigation of the sintered samples reveals an alumina matrix with a grain size of ∼5 μm and two different kinds of pore morphologies, i.e. long elongated pores, which stem from the intergranular spacings during SLS, and intermediate pores, which likely originate from larger polyamide agglomerates in the ball milled powder. Also, QIPing at elevated temperatures is found to be a promising alternative for CIPing at room temperature to increase the final part density. Research limitations/implications Cracks, long elongated pores and intermediate pores remained in the sintered parts. Homogenizing the microstructure of the parts through optimizing the composite starting powder, the deposition during SLS, the SLS parameters and QIPing parameters is essential to overcome these limitations. Practical implications Homogenizing the starting powder mixture and the microstructure of the SLS material is the key issue for producing ceramic parts through indirect SLS. Originality/value Indirect SLS of ceramics has hardly been reported and the combined use of SLS and QIPing is innovative in the field of indirect SLS of ceramics.