Effect of direct energy deposition process parameters on single-track deposits of alloy 718Show others and affiliations
2020 (English)In: Metals, ISSN 2075-4701, Vol. 10, no 1, article id 96Article in journal (Refereed) Published
Abstract [en]
The effect of three important process parameters, namely laser power, scanning speed and laser stand-off distance on the deposit geometry, microstructure and segregation characteristics in direct energy deposited alloy 718 specimens has been studied. Laser power and laser stand-off distance were found to notably affect the width and depth of the deposit, while the scanning speed influenced the deposit height. An increase in specific energy conditions (between 0.5 J/mm2 and 1.0 J/mm2) increased the total area of deposit yielding varied grain morphologies and precipitation behaviors which were comprehensively analyzed. A deposit comprising three distinct zones, namely the top, middle and bottom regions, categorized based on the distinct microstructural features formed on account of variation in local solidification conditions. Nb-rich eutectics preferentially segregated in the top region of the deposit (5.4–9.6% area fraction, Af) which predominantly consisted of an equiaxed grain structure, as compared to the middle (1.5–5.7% Af) and the bottom regions (2.6–4.5% Af), where columnar dendritic morphology was observed. High scan speed was more effective in reducing the area fraction of Nb-rich phases in the top and middle regions of the deposit. The <100> crystallographic direction was observed to be the preferred growth direction of columnar grains while equiaxed grains had a random orientation.
Place, publisher, year, edition, pages
MDPI, 2020. Vol. 10, no 1, article id 96
Keywords [en]
Columnar dendritic morphology, Columnar to equiaxed transition (CET), Constitutional supercooling, High deposition rate, Laser metal deposition (LMD)
National Category
Manufacturing, Surface and Joining Technology
Identifiers
URN: urn:nbn:se:hj:diva-47590DOI: 10.3390/met10010096ISI: 000516827800096Scopus ID: 2-s2.0-85077843217Local ID: GOA JTH 2020OAI: oai:DiVA.org:hj-47590DiVA, id: diva2:1389302
Funder
VinnovaKnowledge Foundation2020-01-292020-01-292021-06-09Bibliographically approved