Effects of process parameters on properties of porous foams formed by laser-assisted melting of steel powder (AISI P21)/foaming agent (ZrH2) mixture. (1st January 2018)

• Record Type: Journal Article
• Authors: Seo, Ja-Ye; Lee, Ki-Yong; Shim, Do-Sik
• Is Part Of: Optics & laser technology. Volume 98(2018)
• Page Start: 326
• Page End: 338
• Publication Date: 2018-01-01
• Subjects: Metal powders -- Direct energy deposition -- Metal foam -- Porosity; Optics -- Periodicals; Lasers -- Periodicals; Electronic journals; 621.366
• DOI: 10.1016/j.optlastec.2017.08.008
• Languages: English
• ISSNs: 0030-3992

Abstract

Highlights: We succeeded to fabricate lightweight metal foams using laser melting deposition. A P21 powder/ZrH2 foaming agent mixture was used to fabricate the metallic foams. The synthesized metal foams exhibited porosities of 10% or lower and a mean pore area of 7 × 10 5 μm 2 . The energy used and powder density control the cooling rate and affect the porosity. The porosity of metal foams was most significantly affected by the powder feed rate. Abstract: This paper describes the fabrication of lightweight metal foams using the directed energy deposition (DED) method. DED is a highly flexible additive manufacturing process wherein a metal powder mixed with a foaming agent is sprayed while a high-power laser is used to simultaneously melt the powder mixture into layered metal foams. In this study, a mixture of a carbon steel material (P21 powder) and a widely used foaming agent, ZrH2, is used to fabricate metal foams. The effects of various process parameters, such as the laser power, powder feed rate, powder gas flow rate, and scanning speed, on the deposition characteristics (porosity, pore size, and pore distribution) are investigated. The synthesized metal foams exhibit porosities of 10% or lower, and a mean pore area of 7 × 10 5 μm 2 . It is observed that the degree of foaming increases in proportion to the laser power to a certain extent. The results also show that the powder feed rate has the most pronounced effect on the porosity of the metal foams, while the powder gas flow rate is the most suitable parameter for adjusting the size of the pores formed within the foams. Further, the scanning speed, which determines the amounts of energy and powder delivered, has a significant effect on the height of the deposits as well as on the properties of the foams. Thus, during the DED process for fabricating metal foams, the pore size and distribution and hence the foam porosity can be tailored by varying the individual process parameters. These findings should be useful as reference data for the design of processes for fabricating porous metallic materials that meet the specific requirements for specialized parts.