Understanding surface roughness of additively manufactured nickel superalloy for space applications

Abstract

Purpose For many applications, including space applications, the usability and performance of a component is dependent on the surface topology of the additively manufactured part. The purpose of this paper is to present an investigation into minimizing the residual surface roughness of direct metal laser sintering (DMLS) samples by manipulating the input process parameters. Design/methodology/approach First, the ability to manipulate surface roughness by modifying processing parameters was explored. Next, the surface topography was characterized to quantify roughness. Finally, microthruster nozzles were created both additively and conventionally for flow testing and comparison. Findings Surface roughness of DMLS samples was found to be highly dependent on the laser power and scan speed. Because of unintended partially sintered particles adhering to the surface, a localized laser fluence mechanism was explored. Experimental results show that surface roughness is influenced by the varied parameters but is not a completely fluence driven process; therefore, a relationship between laser fluence and surface roughness can be incorporated but not completely assumed. Originality/value This paper serves as an aid in understanding the importance of surface roughness and the mechanisms associated with DMLS. Rather than exploring a more common global energy density, a localized laser fluence was initiated. Moreover, the methodology and conclusions can be used when optimizing parts via metal additive manufacturing.

Performance Impacts of Metal Additive Manufacturing of Very Small Nozzles

“…As shown in the experimental additively manufactured nozzles, there are likely multiple defects of varying size throughout the nozzle rather than just a single one at the throat of the nozzle. Images of grooves with similar dimensions in Inconel 718, from Shelton et al (2020), show similar features on dozens of parts, indicating that these are inherent features with the laser sintering LPBF process. These additional defects would add even more wakes and shocks within the nozzle that would lead to further increases in entropy and losses in stagnation pressure.…”

“…The roughness has been further understood by measurements of 0.4-mm-diameter grooves in printed Inconel 718 (Special Metals, Moore, Oklahoma), which exhibited similar average roughness when measured on an LSM (Shelton et al 2020). However, there is a 35% difference in the maximum roughness heights between the two nozzle varieties.…”

“…The LPBF nozzles were manufactured by an outside commercial vendor, using Haynes 282 (Haynes International, Kokomo, Indiana) alloy in EOS M290 printers (Krailling, Germany). While many parameters, such as laser power, scan speed, scan strategy, powder sieving, and reuse, can affect surface quality, as shown in Shelton et al (2020) for cylindrical slots of similar size and printed in a similar alloy, Inconel 718, the specific parameters used by the vendor are considered proprietary information. However, the achieved surface roughness measured in this research, 7.3 μm (Table 1), is near the middle of the range reported by Shelton et al (2020) for Inconel using all new powder.…”

“…While many parameters, such as laser power, scan speed, scan strategy, powder sieving, and reuse, can affect surface quality, as shown in Shelton et al (2020) for cylindrical slots of similar size and printed in a similar alloy, Inconel 718, the specific parameters used by the vendor are considered proprietary information. However, the achieved surface roughness measured in this research, 7.3 μm (Table 1), is near the middle of the range reported by Shelton et al (2020) for Inconel using all new powder. Haynes 282 has a similar composition to Inconel 718, with more nickel and cobalt and correspondingly lower fractions of some other components.…”

Wear Behavior of AlSi10Mg Alloy Produced by Laser‐Based Powder Bed Fusion and Gravity Casting

“…Stainless steel, [5] Ti, [6] Co, [7] Ni, [8] and Al [9] alloys have been widely investigated in the literature, and Cu, [10] Mg, [11] and Au [12] alloys are attracting increased interest. The LPBF technique can be applied in the fields of aerospace, [13] aviation, [14] and automotive [15] industries, as well as the production of robotic components, [16] orthopedic implants, [17] or simple prototypes. [18] Regarding the automotive field, according to the new target to reduce CO 2 passenger car emissions from 2025 to 2030, established by EU regulations, [19] there is a need to further reduce car weight to minimize harmful emissions and improve fuel economy.…”