Effect of Process Optimization Parameters and Hot Isostatic Pressing on Microstructure and Hardness of Additively Manufacture Co-Cr Aerospace Alloy
In the current study, the effect of carefully designed Powder Bed Fusion (PBF) laser parameters on the microstructure and hardness of Co-Cr alloy straight, thin-wall additively manufactured test coupons that are as-built or have undergone Hot Isostatic Pressing (HIP) was investigated. Commercially, it was important to evaluate the relationship between energy density (ED) input (laser power, scan speed) and the microstructure developed in the Co-Cr alloy coupons for an aerospace application. Both the high ED and low ED input processing laser parameters induce a higher percent (%) volume of defects in the as-built coupons when compared to the recommended OEM’s benchmark parameters. However, after HIP, the % volume fraction of defects reduces significantly, and the microstructure is homogenized. Furthermore, the hardness value (strength) of the test coupons manufactured using the recommended OEM’s laser parameters is comparable to those obtained in the low ED input test coupons after HIP; which could be utilized to enhance productivity. In addition, the surface roughness of the low ED input parameter coupons after HIP is similar to the coupons produced using the OEM’s laser parameters assessed with light optical magnification image evaluation. HIP can be an excellent post-processing method to reduce internal Co-Cr defects for a given range of laser energy densities in metal additive manufacturing at increased build speeds.