Atmosphere control at hot isostatic pressing of PM components

Purpose and goal

The project has demonstrated the concept of atmospheric control in hot isostatic presses(HIP) of capsule-free components, manufactured via various press and sinter methods or additive manufacturing. This provides new opportunities for the PM industry to manufacture components with optimized properties, such as surface properties (hardness etc) and bulk properties (correct structure and density). Another aspect of the project was also to evaluate the impact on HIP equipment, where it has been studied how new atmospheres affect, for example, furnace materials in the HIP.

Expected results and effects

In the project, it has been demonstrated how carburization can be carried out in HIP like a conventional case hardening process, with a hard surface accompanied by carburized material. Process map has been produced to demonstrate relationship between process choice and material response. Similarly, nitriding has been studied which is an easier process to optimize, and advantageous due to high nitrogen activities at high pressure in HIP. The hydrogen response has also been studied at high pressures, of interest for a neutral environment and to ensure the safety of the HIP equipment.

Planned approach and implementation

The reaction between different kind of materials from Höganäs, Uddeholm and Quintus (mainly Mo-grades), and atmospheres including carbon, nitrogen and hydrogen gases has been systematically evaluated after HIPing. The information was used to optime the process itself, and to create new possibilities with PM-produced material grades like case hardening or nitriding. Another possibility is to investigate how minor additions of reactive gases can give neutral atmosphere and thereby avoid unwanted oxidation or carbon/nitrogen loss.