In situ detection of cracks during laser powder bed fusion using acoustic emission monitoring

•Crack-related AE activity can be registered by a simple threshold approach.•AE signals from cracks differ from the noise by waveform and statistical parameters.•There is a clear relation between cracks directly observed by µ-CT and AE signals.•The time between a layer was built and a crack emergence can take up to an hour.•AE method enables to detect cracks regardless of their spatial or temporal location.