Effects of cryogenics and case hardening on friction welded SAE 8620 steel parts


Thesis Type: Postgraduate

Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey

Approval Date: 2014

Thesis Language: Turkish

Student: BİLAL KÖYLÜOĞLU

Supervisor: Abbas Tamer Özdemir

Abstract:

In this work, effects of carburizing and cryogenic treatments on the behavior of friction welded SAE 8620 quality steel parts were examined. Some preliminary work was accomplished to determine the best parameters to successfully adjoin the steel parts by friction welding technique. For comparison, as well as friction welded, plain samples were also prepared. All samples were categorized in several groups, where each batch received a specific treatment such as; successive combinations of carburization, cryogenics and annealing treatments, respectively. Some preliminary mechanical testing using tensile testing in accordance with residual stress measurements for welded samples were accomplished simultaneously. However, a direct correlation in between hardness, tensile strength and residual stress distribution could not be found. It is evident that due to severe cutting forces induced during machining of the samples, severe compressive residual stresses were introduced on the surface. After systematic heat treatments, these negative stresses were mostlyfound to increase in the positive sense. On the contrary, welded parts displayed completely different manner of mechanical strength as well as residual stress distributions.