5567.005 Build Area Qualification Through Statistical Modeling of Melt Pool and Defect Distributions

Qualification of melt pool and defect populations via uniform sampling of build area and statistical modeling to identify qualified build regions.

Problem

Laser powder bed fusion (L-PBF) processes have demonstrated difficulties in minimizing defect variability that ultimately plague system-critical applications. Part of this defect variability has been tied to irregularities in inert gas flow over the build area, leading to poor spatter pickup and plume dissipation. Furthermore, the variation in commercial L-PBF system designs leads to unique inconsistencies related to build area effects across L-PBF systems.

Objective

The objective of the project is to characterize process variability through metallography and X-ray computed tomography (XCT), statistically modeled melt pool dimensions and defect size, and number distributions. This project also aims to develop a standard approach to assess and qualify process variability and build regions in LPBF machines.

Technical Approach

The qualification procedure is developed and demonstrated using a Lumex Matsuura 25 LPBF system printing 316L steel. The primary process parameters are laser power, scan speed, hatch spacing, layer thickness, spot size, and scan strategy. This provides a porosity baseline that can be expected in final defect coupons assuming inadequate time for powder gas porosity to escape during in-process melting. Build area qualification begins with defining candidate sampling locations and regions on the build area. The build area center is represented by the centermost sampling locations and is defined as the Center of Performance (COP). The remaining candidate sampling locations will be compared to the COP for qualification. Melt pool dimensions for qualification metrics are acquired via printing of multi-track coupons placed at each sampling location. XCT segmentation data will be performed with conventional image processing techniques and used to generate empirical distributions of defect size for each density coupon. The procedure for build area qualification will be repeated with a compromised gas flow system to demonstrate the build area’s ability to qualify and detect inadequate process regimes. At the end of this project, a documented approach, enabling build area qualification applications for key input (material, machine, parameters) will be dispersed.

Project Participants

Project Principal

Other Project Participants

  • Purdue University

Public Participants

  • U.S. Department of Defense

Project Summary

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