Effect of Process Parameters on the Surface Microgeometry of a Ti6Al4V Alloy Manufactured by Laser Powder Bed Fusion: 3D vs. 2D Characterization

Alberto Molinari,Erica Iacob,Valerio Luchin,Vigilio Fontanari,Simone Ancellotti,Matteo Benedetti,Gianluca Zappini

doi:10.3390/met12010106

Alberto Molinari, Erica Iacob + Show 5 more

Open Access

https://doi.org/10.3390/met12010106

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Journal: Metals	Publication Date: Jan 5, 2022
Citations: 7	License type: CC BY 4.0

Affiliation: University of Trento, Fondazione Bruno Kessler

Abstract

The influence of the main process parameters, laser power, point distance and time exposure, on the surface microgeometry of Ti6Al4V specimens produced by a pulsed powder bed fusion process was investigated. A 3D characterization was carried out and collected data were elaborated to reconstruct the surface and to determine both the 3D and the 2D material ratio curves along different directions. The 3D material ratio curve gives a slightly lower material ratio of peak zone Mr1 and higher material ratio of valley zone Mr2, reduced peak height Rpk and reduced valley height Rvk than the 2D curves. Roughness is greater in the 3D analysis than in the 2D one, skewness is the same and kurtosis increases from <3 in 2D to >3 in 3D. Roughness and skewness increase on increasing point distance and decreasing time exposure and laser power. Within the investigated ranges (27.3–71.2 J/mm3), an increase in energy density reduces the surface roughness while skewness and kurtosis are not significantly affected. The results indicate that a 3D approach allows better characterization of the surface microgeometry than a 2D one.

Highlights

Additive manufacturing (AM) of Ti and its alloys finds broad application especially in the biomedical field, in which surface roughness impacts on properties [1]
The surface microgeometry of parts produced by AM is fundamental to determine the quality of the products
In laser powder bed fusion (LPBF) processes, asperities of solidified layers in the surface parallel to the building plane may collide with the recoating blade causing production interruption [2] or the formation of pores that impair the structural integrity of the final products [3]

Summary

Introduction

Additive manufacturing (AM) of Ti and its alloys finds broad application especially in the biomedical field, in which surface roughness impacts on properties [1]. The surface microgeometry of parts produced by AM is fundamental to determine the quality of the products. It plays an important role in the final properties of the parts, and in their final cost and, the cost competitiveness of the technology. Fatigue strength is influenced by residual stress and porosity, and by surface roughness. Surface defects act as stress raisers, surface finishing aimed at reducing surface roughness extends the fatigue life, as experimentally proved in [4,5]

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