Evaluation of Single Tracks of 17-4ph Steel Manufactured at Different Power Densities and Scanning Speeds by Selective Laser Melting

Abstract

In Selective Laser Melting, the initial units produced are single tracks that overlap to create a single layer; from the sequence of layers, a 3D object is manufactured. The properties of the parts produced by SLM depend heavily on the properties of each single track and each layer formed by these tracks. This study evaluates the effect of processing parameters on the geometrical characteristics of single tracks manufactured from 17-4PH stainless steel powder. A single-mode continuous-wave ytterbium fibre laser was used to manufacture single tracks at laser powers in the range of 100-300 W with a constant spot size of ∼80µm. The single tracks produced were subjected to standard metallographic preparation techniques for further analysis with an optical microscope. Deep molten pool shapes were observed at low scan speeds, while shallow molten pool shapes were observed at high scan speeds. At higher laser power densities, under-cutting and humping effects were also observed. The dimensions of single tracks processed without powder generally decrease with increasing scan speed at constant laser power. However, the geometrical features of the single tracks processed with powder revealed pronounced irregularities believed to be caused by non-homogeneity in the deposited powder layer. OPSOMMINGSelektiewe lasersmelting produseer enkel bane wat mekaar oordek en vorm so ʼn enkele laag. Daaropvolgende lae vorm dan ʼn driedimensionele onderdeel. Die eienskappe van hierdie onderdele word grootliks beïnvloed deur die eienskappe van elke baan en elke laag. Hierdie studie evalueer die effek van die prosesseringsparameters op die geometriese eienskappe van enkel bane wat van 17-4PH vlekvrye staalpoeier vervaardig is. ʼn Enkelmodus kontinuegolf ytterbium vesel laser is gebruik om die enkel bane te vervaardig. Die laser drywing het gewissel van 100 tot 300W met ʼn konstante kolgrootte van ongeveer 80µm. Die enkel bane is dan aan standaard metallografiese voorbereidingstegnieke onderwerp sodat verdere analise met ʼn optiese mikroskoop kon geskied. Diepgesmelte poel vorms is bespeur teen lae skandeersnelhede, terwyl vlakgesmelte poel vorms by hoë skandeersnelhede gewaar is. By hoër laser drywingsdigthede is ondersnyding en hobbelvorming waargeneem. Die dimensies van die enkel bane wat sonder poeier geprosesseer is, het oor die algemeen afgeneem met ʼn toename in skandeersnelheid by konstante laserdrywing. Die geometriese eienskappe van die enkel bane wat wel met poeier geprosesseer is, het noemenswaardige onreëlmatighede aan die lig gebring. Daar word vermoed dat die onreëlmatighede as gevolg van nie-homogene verskynsels in die gedeponeerde poeierlaag is.

Thermal design considerations for a L-PBF built metal component: effects of Inter-Layer Cooling Time, Preheating Temperature and Gas Flow

“…This phenomenon is evaluated through two case studies using nickel-based superalloy Inconel 718 and investigating the effect on two layers thickness, respectively, of 40 and 60 microns. All the results are evaluated through the Melt Pool analysis [31][32][33][34] of several Single and Multi-Tracks [35][36][37][38]. More specifically, it will be investigated if the preheating temperature affects the Melt Pool shape and the Melting regime as a function of the substrate height of the tested specimen.…”

A Supervised Machine Learning Model for Regression to Predict Melt Pool Formation and Morphology in Laser Powder Bed Fusion

“…In every case study, the specimens utilized for the analysis are modeled according to the following specification (Figure 1). In more detail, the specimens are modeled as parallelepipeds of size 10 × 10 × 2 mm, which is suitable to print ten single tracks [2,4,18,[40][41][42][43][44][45][46][47][48][49][50] on a stable consolidated material [36]. The distance between the tracks is established in order to prevent the adjacent melt pool from overlapping, whereas the track length is maintained at 7 mm to provide a steady-state melt pool.…”

“…The ability to melt metal alloys of interest and create custom parts with a high degree of geometrical complexity that otherwise could not have been produced through traditional means led to many technological advancements. A host of technological advancements were made, not just in printing technology and the associated hardware but also in the equally important ecosystem of software tools supporting the manufacturing of viable industry-grade parts [2][3][4].…”

An Automatic on Top Analysis of Single Scan Tracks to Evaluate the Laser Powder Bed Fusion Building Parameters

“…Recently, for a preliminary process parameter screening, a simpler and faster approach has been set up by exploiting Single Scan Tracks (SSTs) [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. The SST corresponds to a laser track scanned on a single powder layer previously spread onto a substrate.…”

“…According to Aversa et al and Yadroitsev et al, the analysis of the geometrical features of an SST cross-section, such as its width, growth, depth and contact angles, can be successfully used to investigate the melting and consolidation behavior of the material and thus its AM processability [ 7 , 17 ]. Furthermore, in many works, the correlation between LPBF parameters and the cross-section morphology was considered to identify the process window [ 7 , 8 , 9 , 17 ]. As reported in Aversa et al, several considerations on cross-section can be made, such as the fact that stable SSTs are usually characterized by similar growth and depth values although low depth or contact angle values can be correlated with incorrect process parameter values [ 7 ].…”