Jul 17, 2017 | By Tess

LPW Technology, a UK-based developer, manufacturer, and supplier of metal powders, recently conducted an investigation into a cracked 3D printed part and found that the defect was caused by powder contamination. The case study, said LPW, shows the “complexity of the AM process” and the importance of following strict procedures for powder maintenance.

We already know that metal 3D printing is a complicated process that requires stringent quality control and monitoring. What people might not realize, however, is that even a slight lapse in these processes can result in devastatingly defected 3D printed parts. This was recently proven through an investigation that LPW Technology conducted into a cracked component 3D printed for an industrial gas turbine application.

According to a recent publication by the UK-based company, one of its clients recently brought it a turbine part made using a selective laser melting (SLM) 3D printing process. The part, made from aluminum AlSi10Mg, exhibited some cracking, and LPW was tasked with figuring out the cause of the defect. The suspect? The metal 3D printing powder.

In order to determine the cause of the defect, LPW first tested a retained sample from the U.S. client’s order. After a full chemical and size analysis was conducted on the sample using LPW’s state-of-the-art equipment, the company found that there was no contamination of the powder that was shipped to the company. Among the processes used to test the metal powder were Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX).

The next step then was to investigate a sample of powder sent from the company, along with the 3D printed part itself. After conducting tests on the company’s powder sample, LPW found that the aluminum powder was, in fact, contaminated. This became clear after EDX testing found foreign Inconel 625 particles dispersed in the aluminum powder.

The contamination, it turns out, was caused during a material change for the SLM 3D printer. That is, LPW’s client realized that its powder feed stock had recently been changed from Inconel 625 to AlSi10Mg by a “relatively junior operator” who had not properly cleaned the SLM equipment.

As LPW stated: “This is a prime example of the complexity of the AM process and how working with the highly experienced LPW team can limit exposure to risk. The customer had been unaware that a few stray particles left from a machine changeover could have such an impact on the part quality.”

How could such a tiny amount of Inconel 625 in the AlSi10Mg powder have such a severe effect? LPW found that the former, which is a nickel alloy, has a “very limited solubility” in aluminum. And while the nickel powder was mostly spread homogeneously throughout the aluminum powder, in some areas it was more concentrated, with wt% in excess of 40%. It was these areas where the parts experienced the most cracking and damage.

All in all, LPW said it only it four days to get to the bottom of its client’s metal 3D printing mystery. It offers its investigation service to all its clients in case of any defects caused by materials.

Posted in 3D Printing Materials

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