Effects of Heat Treatment on Residual Stresses in Additive Manufacturing
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Materials engineering (MPAEM), MSc
Publicerad
Författare
Kristensen, Rasmus
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Metal additive manufacturing (AM) is constantly developing and expanding into new
segments. The automotive industry has so far not implemented AM to any larger
extent. One reason is the relatively high cost of AM-components, but mainly due to
the materials that are available is not used to a larger extent within the automotive
sector e.g. titanium and stainless steel. Powder Bed Fusion–Laser Beam (PBF–
LB), the most developed metal AM-method had, until recently, a limited range of
materials available.
However, recently several low-alloyed carbon-containing steels, that are commonly
used in vehicles and machined components have been developed. One issue with
increased carbon content is that the material has shown to be difficult to manufacture
with PBF–LB. Moreover, heat treatment and its influence on residual stresses,
microstructure and hardness are not yet known.
This thesis focuses on the residual stresses and how they are affected by the heat
treatment on samples printed in a low alloy medium carbon steel, 42CrMo4 (AISI
4140). The heat treatments applied in this thesis were not intended to be optimised
for 42CrMo4, but rather investigate a more industrial approach using relatively
standard heat treatment cycles. After analysing the different heat treated samples
it was found that in a regular quench and temper cycle, the parts achieved similar
hardness as conventionally manufactured 42CrMo4 using the same heat treatment.
Samples exposed to a direct temper cycle, hence just tempered as-printed, showed
promising results in terms of residual stresses. This knowledge may serve as a
basis to further research and development of heat treatment cycles to better utilise
42CrMo4 steels in the automotive sector
Beskrivning
Ämne/nyckelord
Additive Manufacturing , Heat treatment , SEM , XRD , Microstructure , 42CrMo4 , AISI 4140 , PBF-LB , Residual stresses