A Study of Processing and Post-treatments of High γ’ Fraction Nickel Superalloy in Additive Manufacturing
Koski, Marjaana Tuulia (2017)
2017
Materiaalitekniikka
Teknisten tieteiden tiedekunta - Faculty of Engineering Sciences
This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
Hyväksymispäivämäärä
2017-03-08
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-201703131147
https://urn.fi/URN:NBN:fi:tty-201703131147
Tiivistelmä
Direct metal laser sintering (DMLS) has been widely adapted in metal powder 3D-printing among additive manufacturing processes. Almost defect free structures and manufacturing of complicated shapes with good surface quality are some of many ad-vantages of DMLS process.
MAR-M247 is a non-weldable nickel-base superalloy. Its creep resistance and thermal stability makes it a suitable material for manufacturing of demanding aerospace compo-nents. In MAR-M247 aluminium and titanium rich gamma prime phase precipitates inside the nickel matrix. Also the amount of Al and Ti predisposes the material for weld cracking. DMLS building process optimization is a paramount in order to study materi-al’s susceptibility to defect formation.
The scope of the thesis was to perform experimental trials on buildability of MAR-M247LC. The main process parameters, scanning speed, power and hatch distance, were varied. By analysing the defect formation, suitable process window was optimized.
Significant reduction of crack formation was observed although formation of other de-fect types might result from insufficient melting. Additional tests on modified laser ex-posure strategies were performed, through increased spot size and multiple exposures. Based on results, second scanning brought additional improvements, although further experiments are required to fully understand the phenomena behind the material’s be-haviour.
Finally, solution and precipitation treatments were performed for as-manufactured sam-ples. Standard heat treatments based on conventional cast procedures homogenized the structure. On the other hand, healing of defects was not investigated.
For future research a closer look at the microstructure would give valuable information on as-manufactured condition. The as-manufactured condition differs greatly from cast structure. Therefore, adjustments on cycle holding times and temperatures are required.
MAR-M247 is a non-weldable nickel-base superalloy. Its creep resistance and thermal stability makes it a suitable material for manufacturing of demanding aerospace compo-nents. In MAR-M247 aluminium and titanium rich gamma prime phase precipitates inside the nickel matrix. Also the amount of Al and Ti predisposes the material for weld cracking. DMLS building process optimization is a paramount in order to study materi-al’s susceptibility to defect formation.
The scope of the thesis was to perform experimental trials on buildability of MAR-M247LC. The main process parameters, scanning speed, power and hatch distance, were varied. By analysing the defect formation, suitable process window was optimized.
Significant reduction of crack formation was observed although formation of other de-fect types might result from insufficient melting. Additional tests on modified laser ex-posure strategies were performed, through increased spot size and multiple exposures. Based on results, second scanning brought additional improvements, although further experiments are required to fully understand the phenomena behind the material’s be-haviour.
Finally, solution and precipitation treatments were performed for as-manufactured sam-ples. Standard heat treatments based on conventional cast procedures homogenized the structure. On the other hand, healing of defects was not investigated.
For future research a closer look at the microstructure would give valuable information on as-manufactured condition. The as-manufactured condition differs greatly from cast structure. Therefore, adjustments on cycle holding times and temperatures are required.