In situ Selective Nitriding Using an Open Source Laser Powder Bed Fusion System
Conventional forms of nitriding titanium limit the locations to surfaces, limiting applications to simple coatings. Additive manufacturing methods provide the opportunity for surface coating methods to be utilized in a layer by layer fabrication method and increase the uses of nitrides. Laser powder bed fusion (LPBF) in particular, provides a fabrication environment with sufficient energy to allow for material nitriding as well as the flexibility of being able to utilize a variety of materials and shielding gases for processing. This project utilizes an AconityONE open source LPBF system with custom laser parameter settings to fabricate and nitride Ti-6Al-4V substrates. This process was tested by nitriding wrought samples of titanium to develop parameter settings that would allow for a consistent repeatable process yielding results that could be later integrated into a single process of fabrication and nitriding. Initial nitriding of wrought samples provided promising results in for form of TiN dendrite formation on samples with successful bonding to the titanium substrates. These laser parameters were varied by changing laser parameters such as laser power, scanning speed, and defocus of the laser beam. The transition from nitriding wrought titanium samples to fabricating and nit riding samples required the consideration of the effects of the fabrication parameters as well as the nitriding parameters to ensure that nitrided regions will provide mechanical properties similar to those exhibited in the nitriding of previous samples. Sandwich build were utilized to evaluate the effects of single nitride layers within fabricated substrates and their effects on samples integrity. These samples allowed for the optimization of fabrication parameters to help focus on the optimization of the nitride process. Surface nitriding was utilized to help narrow down how changes to individual nitride parameters such as laser power, scan speed, beam defocus, and overlap affect the overall quality of the nitride layer.
Navarro, Andres Gerardo, "In situ Selective Nitriding Using an Open Source Laser Powder Bed Fusion System" (2019). ETD Collection for University of Texas, El Paso. AAI22620267.