In many cases powder metallurgy (PM) offers the most cost efficient way to make components on a larger scale, for instance in automotive applications. Complex shapes can be compacted near net shape and reduce the overall number of process steps required for manufacturing. Other benefits of PM include the elimination of scrap, where up to 98% of the raw material goes into the final component, and the possibility to tailor material compositions for specific applications.

A drawback of the PM technology is the inherent 5–15% of porosity in the components, which decreases the strength of the material compared to full density wrought steels. Techniques such as powder forging or rolling densification can be used to reduce or remove porosity in various components to improve strength. It is also possible to use hot isostatic pressing (HIP) to make fully dense parts from powder. A previous investigation, see for instance MPR Volume 72, number 2, 2017, demonstrated for instance that a HIP:ing a PM steel reduced the wear of a dog clutch of a rally car compared to the standard steel mating part. However, HIP:ing normally requires the powder to be included in a canister during the process, which is normally a very expensive process.

The idea, is therefore, to combine pressing and sintering of conventional PM technology with a subsequent HIP:ing step to remove the remaining porosity. If the part is made to a sufficiently high density before the HIP step to have closed porosity the canister is not necessary, thus combining the advantages of conventional PM and HIP.

This paper summarizes the project HIPGEAR, which was run as a part of the Swedish FFI program between 2014 and 2018, and included a number of partners from industry and academia. The purpose of the project was to develop the can-less HIP process. The ultimate goal was to manufacture and test a demonstrator gear looking at applications for trucks.

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