| About this Abstract |
| Meeting |
2024 AWS Professional Program
|
| Symposium
|
2024 AWS Professional Program
|
| Presentation Title |
Experimental Characterization and Kinetic Modelling of the Microstructure Development During L-DED of Type 420 Martensitic Stainless Steel |
| Author(s) |
Zhe Lyu, Thomas J. Lienert, Leijun Li |
| On-Site Speaker (Planned) |
Leijun Li |
| Abstract Scope |
Martensitic stainless steels are often used for hard-facing applications because of their superior wear and corrosion resistance. However, they are also known for their poor weldability due to cold cracking. Laser-DED was used to produce two additive-manufactured deposits that were free of cracks with Type 420 martensite stainless steel powder. One of the builds was deposited with a preheat of 500 ℃ while the other one was with a preheat of 25 ℃. The last pass of the 500 ℃ preheat build had an average hardness of 792±48 HV0.2; the last pass of the 25 ℃ preheat sample had a much lower average hardness and higher standard deviation, 453±120 HV0.2. This significant variation in hardness suggested a heterogeneous microstructure.
With EBSD, the prior austenite was constructed and confirmed the δ to γ, and γ to martensite solid-state transformations. The 500℃ preheating temperature produced a homogenous microstructure of tempered martensite. The other sample with 25 ℃ preheat showed the deposit consisting of three phases in equal fraction, including martensite, austenite, and δ-ferrite. This mixed microstructure has a much lower average hardness with higher variation. The elemental segregation was also more significant in the 25 ℃ sample. To rationalize the microstructure evolution during the laser-DED, the phase transformation kinetics during solidification and the solid-state transformations were computed using the diffusion module of ThermoCalc, DICTRA. The model accurately predicted the microstructure amounts of the final deposits for both preheating cases. The simulated segregation profiles seem to suggest that the solidification segregation plays a significant role in the solid-state segregation at lower temperature range. |
| Proceedings Inclusion? |
Undecided |