Research project shows improved surfaces and durability of additively manufactured components through pack cementation

A recently completed research project by Neue Materialien Bayreuth GmbH demonstrated that pack cementation can significantly improve the surface roughness as well as the hot corrosion and oxidation resistance of additively manufactured components. These findings originate from the IGF research project “SLM-Pack”, which was carried out in collaboration with the Dechema Research Institute (DFI).

Additive manufacturing, in particular the Laser Powder Bed Fusion (L-PBF) process, offers the possibility of producing components with almost unlimited geometries quickly and independently of traditional process chains. However, the printed components often exhibit high surface roughness and near-surface defects that impair their oxidation resistance and mechanical properties, especially fatigue strength. To compensate for these disadvantages, complex post-processing operations such as sandblasting and grinding are usually required, which is particularly time-consuming for complex geometries.

The pack cementation process, a chemical vapor deposition (CVD) method, has been used for decades to produce protective coatings on metallic surfaces. These layers, rich in chromium, silicon or aluminum, significantly improve the hot corrosion and oxidation resistance of high-temperature alloys. The challenge and goal of the “SLM-Pack” project was to investigate the applicability of this process to additively manufactured components.

The research results are very promising. Pack cementation reduced the surface roughness of the aluminized samples of all the alloys investigated by 20%. In addition, there was a significant improvement in fatigue life compared to conventionally manufactured alloys, as the aluminum diffusion layer prevents the propagation of cracks. Another significant advantage was the increased oxidation resistance of the components, which formed a protective Al2O3 layer even at temperatures of up to 1,000°C. The oxidation resistance of an L-PBF-printed alloy 625 improved fivefold, and even seventeenfold in the case of alloy 718.

The project “SLM-Pack – Surface finishing of additively manufactured components: Improvement of mechanical properties and oxidation behavior” was funded by the Industrielle Gemeinschaftsforschung IGF (funding code 21431 N). These results offer new perspectives for the industrial application of additively manufactured components, particularly in areas that place high demands on material durability and performance.