Laser Metal Deposition of Aerospace Alloys: Production of Mechanical Testing Specimens and Future Developments

Laser Metal Deposition (LMD) has been utilized in the aerospace industry to create near net shape components.  Quantifying the mechanical properties of these parts is important to understand how they will perform in service, such as at high temperature, or during dynamic, cyclical loading conditions.

An Optomec 850-M Laser Engineered Net Shaping^TM (LENS) machine was used to create near-net shape round tensile bars using 316L stainless steel powder as a baseline for other materials such as IN625 and Ti-6Al-4V.  Dimensions of the tensile bar columns were 4.75” tall with 0.375” diameter grip section and a 0.25” diameter reduced section.  Results from all-wrought 316L LENS^TM builds were compared to all-wrought 316L bars machined with the same geometry.  Microstructure analysis revealed that the majority of the build consisted of cellular austenite, which is consistent with a melting and re-solidification process. 

Future developments include the production of tensile bars and fatigue specimens using more aerospace-relevant materials such as Inconel 625 and Ti-6Al-4V.  The effect of strain rate and stress amplitude on the mechanical behavior of these materials will provide essential information required to qualify these materials and processes for more widespread industrial use.