Femtosecond laser post-processing of metal parts produced by laser additive manufacturing

Abstract

High-repetition rate femtosecond laser radiation was utilized to improve surface quality of metal parts manufactured by laser additive techniques. This novel approach can be used to postprocess parts made of heat-sensitive materials, and to attain the designed net shape with micrometer precision. SummaryLaser Additive Manufacturing (LAM) is a cutting-edge manufacturing approach that is based on consecutive application of material layers and the transfer of geometrical information from the digital design data to the resulting near-net shape [1]. Laser Metal Deposition (LMD) and Selective Laser Melting (SLM) are the two well-established LAM techniques that utilize serial powder materials including superalloys, ceramics, and multi-material compounds e.g. wear and thermal protective coatings [2]. Given the near-net shape nature of LAM, a certain amount of mechanical post-processing, i.e. CNC milling, is required to improve the surface finish and the consistency with the design data.Femtosecond laser machining is an established micro-processing technique that makes advantage of the ultrafast deposition of the optical energy into the material. By using laser pulses with sub-picosecond duration, the heataffected zone at the workpiece can be significantly reduced compared to longer pulses, and various heat-sensitive materials can be processed with sub-micron precision [3].In this paper we present our study of femtosecond laser post-processing of different components manufactured by SLM and LMD from Ni-base superalloys. Various 3D-shaped metal parts made of IN718 and IN625 superalloys were irradiated with tightly focused femtosecond laser light (Amplitude Satsuma, t p <400 fs, λ=1030 nm, f rep = 0.5-5 MHz). Different scanning approaches were used to increase the ablation efficiency at flat and curved surfaces of the workpiece. Laser pulse energy was varied to optimize the resulting surface finish and geometrical consistency. Surface roughness was determined before and after the processing.

Densification behavior, microstructure evolution, and wear property of TiC nanoparticle reinforced AlSi10Mg bulk-form nanocomposites prepared by selective laser melting

“…Selective laser melting (SLM), as a newly developed direct digital manufacturing technology, has been treated as one of the most effective powder-based additive manufacturing (AM) methods for metal parts. [10][11][12][13][14][15][16][17] During SLM process, the 3D parts are built by selectively fusing and consolidation of the thin layers of powder using the high-energy laser beam in a layer-by-layer manner according to the computeraided design (CAD) models of the parts. Because of the unique processing mechanisms of SLM, e.g., a full melting of powder materials followed by a rapid solidification at a rate up to10 6 -10 8 K/s, 18 the molten materials tend to experience a particular nonequilibrium metallurgical process during SLM processing, thereby providing a capacity to produce unique aluminum-based nanocomposite parts.…”

Femtosecond Laser-Based Additive Manufacturing: Current Status and Perspectives

“…A.Y Vorobyev (2007) performed surface treatment of Ti utilising an fs laser, and they were able to produce a large variety of nanostructures on the surface of Ti material with sizes less than 20 nm [196]. also reported the utilisation of an fs laser to improve the surface quality of additive manufactured of Ti-and Ni-based alloy parts [49]. Jiao et al (2018) observed that fs laser processing on Ti6Al4V material produced nanostructures that paved the way for AM part self-cleaning and hydrophobic properties [199].…”

“…As fs laser sources are capable of producing precise features at the micro and nano levels in a highly localised and controlled manner, applications at the nanomanufacturing processes [30], and micro fabrications (e.g., fabrication of micro-needles for medical applications [46]) are among the most commonly explored in the literature [47,48]. In addition, various works have explored the potential use of fs lasers for post-processing of 3D printed metallic components (i.e., utilising the associated heat to alter the microstructure) [49,50]. Further, fs laser sources were utilised to modify the flexural strength and surface morphology of materials such as translucent monolithic zirconia (for dental restoration) [51].…”

Impact of chemical polishing on surface roughness and dimensional quality of electron beam melting process (EBM) parts

“…To improve surface finish of metal powder bed processes, some finishing operations are needed such as traditional machining [5,6], shot-peening [7,8,9], tribofinishing / vibratory finishing [10], laser polishing [11,12,13,14,15,16,17,18,19,20,21,22], chemical polishing and electrolytic polishing [5]. In this study, the focus is set on chemical polishing.…”