Precipitation Process in Additively Manufactured Maraging 300
Typ
Examensarbete för masterexamen
Program
Publicerad
2021
Författare
Hermansson, Erik
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The precipitation process of maraging 300 steel produced with Laser Powder Bed
Fusion, (LPBF), was examined using atom probe tomography. To achieve this,
samples were subjected to an aging heat treatment at 500 °C for 15 min, 30 min and
180 min, in addition a sample from the as-built block was also analysed. In the
as-built condition initial precipitation of Ni3(Ti, Mo) was detected together with a
clustering of nickel and titanium. When aged for 15 minutes the sample showed
more developed Ni3(Ti, Mo)-spheres as well as Ni3(Mo, Ti)-rods. There was also
very slight precipitation of the Fe7Mo6 μ-phase at points of intersection between
these rods. Upon further aging the Ni3(Ti, Mo)-spheres generally decreased in size
while the Ni3(Ti, Mo) formed larger precipitates of both plate- and rod-configuration.
The μ-phase saw drastic increases in its size and number density upon aging for 180
minutes. It was still only found in connection with Ni3(Mo, Ti)-rods, indicating that
it had formed from these. At the same time there was some new Ni3(Ti, Mo)-phase
created as part of the Ni3(Mo, Ti)-rods. This is likely a consequence of the μ-phase
attracting molybdenum from the rods. As this transfer of molybdenum could start
diminishing the size of the rods and the rods were at their largest at 180 minutes,
it is likely the rods that contribute the most to the strength of the steel, as the 3
hour aging time is the one suggested in the literature for optimum strength.
Beskrivning
Ämne/nyckelord
maraging 300 , APT , precipitate , additive manufacturing , LPBF , Maraging , Age-hardening , 18Ni300