Evidence of in-situ Cu clustering as a function of laser power during laser powder bed fusion of 17-4 PH stainless steel

The use of intrinsic heat treatments to control the microstructural evolution during additive manufacturing could eliminate the need for costly post-build processing. Using atom probe microscopy and cluster search algorithms, this study investigates the degree of Cu clustering and precipitation in 17-4 precipitate hardening (PH) stainless steel fabricated by laser powder bed fusion (LPBF). It was found that LPBF samples exhibit a greater than random degree of Cu clustering, irrespective of the laser power during fabrication. It is further shown that using a higher laser power (161.5 W rather than 127.5 W) led to a higher number density of Cu clusters, Cu precipitates, and higher hardness due to the greater heat input. The observations of Cu-rich clusters and precipitates within as-printed LPBF samples and its laser power dependence are novel and show potential for inducing desired strengthening phases directly during LPBF, mitigating the need for post-fabrication heat treatments.

Automated summary

The use of intrinsic heat treatments during additive manufacturing can eliminate the need for costly post-build processing. This study investigates the clustering and precipitation of copper in 17-4 PH stainless steel fabricated by laser powder bed fusion. The results show that the samples exhibit a higher degree of copper clustering and precipitation, and using a higher laser power leads to a higher density of copper clusters and precipitates. These findings demonstrate the potential for inducing desired strengthening phases directly during the fabrication process.