Invited Review Article: Review of the formation and impact of flaws in powder bed fusion additive manufacturing

It is widely accepted that gas porosity and lack-of-fusion flaws can degrade both static and dynamic mechanical performance of additively manufactured components, limiting the use of AM components in critical applications. However, the mechanisms by which these flaws form are still debated, and their impact on dynamic material performance have yet to be fully quantified. This work outlines the current understanding of the formation mechanisms for gas porosity, lack-of-fusion, and flaws related to melt pool instabilities. Where possible, the spatial and morphological characteristics of these flaws are highlighted, as well as their impact on mechanical properties. The effect of hot isostatic pressing is also discussed.