Microstructural evolution in additive manufacturing with high power lasers: Deposition, characterization and performance

High power lasers provide time and cost effective method for metallic surface modification. In this work these modifications are explored as: 1) a simple melting and subsequent rapid solidification of a metallic surface – resulting in superior properties post-treatment; 2) deposition of an additional metallic layer on top of exiting metallic surface with an excellent metallurgical bonding which can function as a protective coating and/or be used to construct 3D structures. A simple model for the prediction of a resulting geometry of the laser based metallic deposition is presented which is able to make predictions based entirely on initial processing parameters (which can easily be tuned) with applications towards 3D printing and tool repair. The particular industrial application of this works centres on steel manufacturing process, where the laser re-melting and laser based metallic deposition is used to improve the performance of rolls that deliver slab metal during steel production. Solutions to a number of existing challenges are presented such: superior wear resistance, dramatic reduction in build-up of undesirable material. Additionally a guidelines are presented for both understanding the build-up mechanism and thermal degradation of metal which are linked to microstructural and elemental properties – thus providing an understanding how to address new challenges in the future.