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Effect of post treatments on electron beam melting built Alloy 718 produced with different microstructures
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
2019 (engelsk)Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
Abstract [en]

Additive Manufacturing (AM) is a process that enables production of intricate geometries with difficult to machine materials. Therefore, production of hard materials like Alloy 718 by metal AM techniques like Electron Beam Melting (EBM) has been grabbing attention lately. This has created significant interest in investigation of EBM built Alloy 718. The as-built EBM Alloy 718 has concerns like presence of inevitable defects, microstructural heterogeneity, etc. Also, EBM Alloy 718 has not been fully explored for production of specimens with different microstructures. This has fuelled interest in post treatment of EBM built Alloy 718 produced with different microstructures.

The as-built specimens with different microstructures were subjected to two post treatments namely Hot Isostatic Pressing (HIP) and HIP followed by Heat Treatment (HT). The effect of these treatments was analysed for defect content, grain structure, hardness and different phases in the specimens. The variation in carbide size amongst as-built samples can be attributed to different cooling rates during solidification and thus primary dendrite arm spacing. Subjecting the specimens to HIP led to significant reduction in defect content and dissolution of the δ phase. After HIP, samples showed tendency for abnormal gain growth in equiaxed region and not in columnar region. Solution treatment step in HIP+HT led to more precipitation of grain boundary δ phase in bigger grains than smaller ones in the same sample. Hardness values of samples were reduced after HIP which was attributed to dissolution of γ'' phase. However, hardness was increased beyond as-built values after HIP+HT, which was attributed to reprecipitation of γ'' phase during aging step.

sted, utgiver, år, opplag, sider
2019. , s. 38
Emneord [en]
Additive manufacturing, electron beam melting, Alloy 718, post treatments, different microstructures
Emneord [sv]
Additiv tillverkning, elektronstrålsmältning, Alloy 718, efterbehandlingar, mikrostrukturer
HSV kategori
Identifikatorer
URN: urn:nbn:se:hv:diva-14531Lokal ID: EXM902OAI: oai:DiVA.org:hv-14531DiVA, id: diva2:1359572
Fag / kurs
Mechanical engineering
Utdanningsprogram
Produktionsteknik, magister
Veileder
Examiner
Tilgjengelig fra: 2019-10-17 Laget: 2019-10-09 Sist oppdatert: 2019-10-17bibliografisk kontrollert

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