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Accessible Unlicensed Requires Authentication Published by De Gruyter October 2, 2017

Statistical analysis of weld bead geometry in Ti6Al4V laser cladding

Comparison of central composite design and five step full factorial test plan

Statistische Analyse der Schweißraupengeometrie von Ti6Al4V beim Laserbeschichten
Angelina Marko, Benjamin Graf and Michael Rethmeier
From the journal Materials Testing

Abstract

The process of laser cladding has become more important during recent years because of its broad application for cladding, repair or additive manufacturing. In the field of mechanical engineering, one use is the repair of turbine blades. For high quality and reliability of the repaired components, it is necessary to adjust the weld bead geometry to the specific repair task. The bead geometry influences the metallurgical bonding and the degree of dilution as well as the formation of defects like pores or cracks. Therefore, it is important to know the effects of the different parameters on the welding bead. A valuable tool to meet this industrial challenge is the design of experiments (DoE). In this context, the user can choose between a huge number of test plans. Greater profit of information is expected by a larger test range. In order to confirm the acceptance, a five-step full factorial test plan is compared to a central composite design in this paper. Moreover, the limits of the experimental range are indicated and restrictions can be derived. As the results show, the essential effects are detected with a full factorial test plan as well as with a central composite design. Merely the effect strength could not always be specified unambiguously. On this account and in consideration of cost efficiency, the use of central compound design is recommended in industrial applications.

Kurzfassung

Die Bedeutung des Laser-Pulver-Auftragsschweiß-Prozesses hat in den letzten Jahren enorm zugenommen, da er vielfältig eingesetzt werden kann. Ein Beispiel hierfür ist die Reparatur von Turbinenschaufeln. Um eine hohe Qualität und Zuverlässigkeit hierbei zu gewährleisten, ist eine Anpassung der Schweißraupengeometrie an die jeweilige Reparaturaufgabe notwendig. Die Schweißraupengeometrie beeinflusst die metallurgische Verbindung und den Grad der Aufmischung sowie eventuelle Anbindungsfehler. Aus diesem Grund ist es wichtig, die Effekte der unterschiedlichen Parameter auf die Spurgeometrie zu kennen. Ein bewährtes Werkzeug hierfür ist die statistische Versuchsplanung (DoE). Hierbei kann der Nutzer jedoch zwischen einer Vielzahl von Versuchsplänen wählen. Es wird davon ausgegangen, dass bei größeren Versuchsräumen ein höherer Informationsgewinn erfolgt. Aus diesem Grund wird in dieser Arbeit ein vollfaktorieller Versuchsplan, der in fünf Stufen variiert wird, mit einem zentral zusammengesetzten Versuchsplan (CCD) verglichen. Außerdem werden Grenzen des Prozesses aufgezeigt und der Versuchsraum entsprechend durch Eingrenzungen angepasst. Die Ergbnisse zeigen, dass sowohl der vollfaktorielle Versuchsplan als auch der zentral zusammengesetzte Versuchsplan die wichtigsten Effekte aufzeigt. Lediglich die Effektstärke kann durch den CCD-Versuchsplan nicht eindeutig bestimmt werden. Für den industriellen Einsatz wird daher unter Berücksichtigung der Kosteneffizienz der Einsatz eines CCD-Versuchsplanes empfohlen.


*Correspondence Address, Angelina Marko, Fraunhofer Institute for Production Systems, and Design Technology IPK, Pascalstraße 8–9, 10587 Berlin, Germany, E-mail:

Angelina Marko, born in 1987, received her MSc degree in Production Technology from TU Berlin, Germany in 2015. After some practical experiences as quality engineer in the industry, she has been a scientific assistant at Fraunhofer Institute for Production Systems and Design Technology IPK, Berlin, since 2016. Her research focus is on laser metal deposition and quality management.

Benjamin Graf studied Mechanical Engineering at TU Berlin, Germany and received his diploma degree in 2010. After his studies, he started working at Fraunhofer IPK, Berlin in the department for Joining and Coating Technology. His technological working field comprises laser metal deposition with its applications in wear protection, repair and additive manufacturing. He is Head of the department for joining technology at Fraunhofer IPK.

Prof. Dr.-Ing. Michael Rethmeier, born in 1972, studied Mechanical Engineering at TU Braunschweig, Germany. Afterwards, he worked at the same university where he received his PhD in 2003 and then became project manager for production engineering and concepts at Volkswagen AG group research. In 2007, he received his full professorship at TU Berlin in combination with being Head of the division “Safety of Joined Components” at the Federal Institute for Materials Research and Testing BAM in Berlin. Additionally, he is Division Director of “Joining and Coating Technology” of the Fraunhofer Institute for Production Systems and Design Technology IPK in Berlin.


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Published Online: 2017-10-02
Published in Print: 2017-10-04

© 2017, Carl Hanser Verlag, München