Phase transformation under isostatic pressure in HIP

ABSTRACT

The new HIP cooling systems enable very fast cooling rates under isostatic pressure. This does not only enable shorter HIP cycles but also allows complete heat treatment cycles to be performed in one HIP cycle. It has been shown in previous studies that extreme pressures of several thousand bar can push phase transformation towards longer times. The new URQ HIP cooling systems give the opportunity to investigate the impact of pressures up to 2000 bar on phase transformation time dependency. For each of the two materials in this study, a comparison of austenite phase transformation time at 100 and 1700 bar was performed. The study was performed by isothermal heat treatment of specimens for a specific time followed by quenching. To evaluate the influence of pressure on hardenability, the phase fractions were evaluated using grid method on SEM images. The study found significant influence of HIP pressure on hardenability.

KEYWORDS:

• HIP
• isostatic
• pressure
• phase transformation
• austenite
• perlite
• microstructure
• URQ

Acknowledgements

Quintus Technologies AB are especially acknowledged for their contribution of performing all HIP cycles within the project and for supplying material. Höganäs AB is also acknowledged for supplying material specimens to the project.

Notes on contributors

Alexander Angré graduated from The Royal Institute of Technology, Stockholm, Sweden, with a Master of Science in Materials Science in 2009. Has since 2010 been working with applied research with the Swedish powder metallurgy industry, as part of the Powder Materials group at Swerea KIMAB. Research Leader of the above mentioned group since July 2016.

Magnus Ahlfors graduated from Chalmers University of Technology in 2012 with a Master of Science in Materials Engineering. Magnus has since then worked with structural calculations and for the last 3 years as an applications engineer for isostatic pressing at Quintus Technologies AB.

Dimitris Chasoglou studied Physics in Aristotle University of Thessaloniki, Greece until 2006. Obtained his MSc in Advanced Engineering Materials from Chalmers University of Technology, Gothenburg, Sweden in 2008. For his research on the surface characteristics of low alloyed steel powders he obtained his PhD from the same institute in 2012. Started working as a researcher on the Powder Metallurgy group in Swerea KIMAB, Stockholm, Sweden in 2012 and since 2014 he is working as a Senior Material Development Engineer in Höganäs AB, Höganäs, Sweden.

Linn Larsson graduated from The Royal Institute of Technology, Stockholm, Sweden, with a Master of Science in Materials Science in 2008. Has since 2008 been working at Sandvik with materials research as part of the SMT Powder Technology R&D group.

Erik Claesson graduated from The Royal Institute of Technology, Stockholm, Sweden, with a Master of Science in Materials Science in 2014. Has since 2015 been working with applied research with the Swedish powder metallurgy industry, as part of the Powder Materials group at Swerea KIMAB.

Oskar Karlsson graduated from The Royal Institute of Technology, Stockholm, Sweden, with a Master of Science in Materials Science in 2002. Has since then been working in the Metallography group at Swerea KIMAB. Senior researcher.

ORCID

Magnus Ahlfors http://orcid.org/0000-0003-1330-0558

Dimitris Chasoglou http://orcid.org/0000-0002-9510-4368

Oskar Karlsson http://orcid.org/0000-0003-4679-9535

Additional information

Funding

This work has been financed by the member companies of the Powder Materials Member Research Consortia at Swerea KIMAB and RISE. The members of the research committee of the project: Magnus Ahlfors at Quintus Technologies AB, Stefan Sehlstedt at Quintus Technologies AB, Dimitris Chasoglou at Höganäs AB, Linn Larsson at AB Sandvik Materials Technology, Martin Östlund at AB Sandvik Materials Technology are greatly acknowledged for their contribution and for stimulating discussions.