An Investigation on the Microstructure and Hardness of Martensitic Stainless Steel in Repair Welding Method

, M.Sc. Thesis Sharif University of Technology Tehrani, Morteza (Author) ; Kokabi, Amir Hossein (Supervisor) ; Madah Hoseini, Hamid Reza (Co-Advisor)

Abstract

Repair welding is one of the important maintenance processes that include build-up welding and surfacing.In this study, investigation of repair welding parameters has been conducted to achieve desired microstructure with the appropriate toughness and minimum residual stress.In this research, local post-weld heat treatment has been performed by Tungsten electrode arc on weld zone. Performing this process with optimum parameters leads to the best heat cycle with the tempered Martensite microstructure. Residual stress of the sample will be reduced. HAZ coarse grains will be refined to finer grains which result in to improved toughness and reduced hardness to the acceptable limit.
Results...

Creating a Protective Coating Against Corrosion and Erosion on the Surface of the Parts using in Sour Environments

, M.Sc. Thesis Sharif University of Technology Ghasemi Tabasi, Hossein (Author) ; Kokabi, Amir Hossein (Supervisor)

Abstract

A concern in the production sour oil and gas is the corrosion caused by the acid gas H2S. Even though corrosion resistant alloys (CRA) have long been available as a material selection option that mitigates H2S corrosion, the carbon steel is in general more cost-effective for oil and gas facilities. The aim of this study is to investigate the mechanical properties of 410NiMo cladding on a low alloy steel substrate. In this investigation, two successive layers of ER410NiMo were clad on low alloy steel substrates. To reduce the likelihood of Hydrogen Induced Cracking (HIC) and producing stable hydrogen traps, Post Weld Heat Treatment (PWHT) was used. To characterize the mechanical properties of...

Improving the Failure Behavior of High Strength and High Hardenable Steels Resistance Spot Welds

, M.Sc. Thesis Sharif University of Technology Aghajani, Hamid Reza (Author) ; Pouranvari, Majid (Supervisor)

Abstract

Selecting materials is a key stage for designing vehicles. Today, advanced high-strength steels and stainless steels are attractive by the automotive industry. In this study, the improvement of mechanical properties of the martensitic stainless steels (MSS420 with annealed condition) and advanced high strength martensitic steels (MS1400 with quenched condition), which have a different response to mechanical tests, were investigated. The welding of MSS420 steel was carried out in three phases. In the first phase, the MSS420 double pulse welding with variable second pulse times (0.2s-1.8s) with a constant secondary pulse current of 4 kA and in the second phase a double pulse welding with...

The Effects of Retrogression and Aging Heat Treatment on the Mechanical Properties and Flow Limit Diagrams of Precipitation-harden-Able Aluminum Alloy

, M.Sc. Thesis Sharif University of Technology Abazari, Mostafa (Author) ; Karimi Taheri, Ali (Supervisor) ; Kazeminejad, Mohsen (Supervisor)

Abstract

Demand for high performance components has caused a propensity towards high strength alloys, especially 7000 series, having extended applications in aerospace, automotive and medical industries. Due to high strength, heat treatability, and optimum weight, these alloys have been implemented in various conditions, specifically AA7075, being directly used in airframes. Through the years, numerous attempts have been made to improve the corrosion and formability properties of these alloys, resulting in the development of various tempering methods such as retrogression and re-ageing. Despite achiving optimal properties, it has been of less interest through literature to assess the formability of...