SUMMARYThe performance simulation of heat recovery steam generators in a cogeneration system has been investigated to see the effect of pinch and approach points on steam generation and also on temperature profiles across the heat recovery steam generator. The effects of operating conditions on steam production and also on exit gas temperature from the heat recovery steam generator are discussed. Low pinch point results in improved heat recovery steam generator performance due to reduced irreversibilities. The supplementary firing enhances the steam production.

Welding of Nickel Based Super Alloys has been challenging due to the cracking and microstructure segregation of alloying elements. These super alloys are often used in extreme environments like in Turbine Blades, Boilers of Waste incinerators, Seals, Turbocharger rotors, high temperature fasteners, pressure vessels etc. The major application include Aerospace and Automobile Industry. The current paper will cover the relevant published work on welding processes and the challenges that were faced to weld nickel based super alloys. The review will go on to describe the weldability, microstructure and mechanical properties that are produced during and after the welding process. This paper will mainly focus on nickel based super alloys and poses many challenges which need to be focused and solved to produce an operational system in an acceptable time frame.

In this review article, research papers related to recent developments in Ni-superalloy technologies have been reviewed in order to provide an insight into recent achievements and the potential for further study, research, and development in this field. In this paper, studies on various aspects of Ni-based superalloys are reviewed, such as production methods, which include widely used casting methods, as well as unconventional alternative procedures, novel techniques, or simulation and prediction of certain alloy casting properties. Reviewing was done by categorising the papers into 4 major categories: manufacturing of Ni-based superalloys, effects of alloying elements, physical and mechanical properties of Ni-based superalloys, and defects in Ni-based superalloys. The process used to make Ni-superalloy parts can have a huge impact on the production process efficiency, the final product’s quality and properties, and the defects formed in it. Investment casting is one of the most common methods for making Ni-superalloy parts. Manufacturing covers studies on various casting methods used to make Ni-based superalloy components, novel techniques and methods developed to improve casting procedures to produce better products, and alternative manufacturing methods like AM and HIP processing. Similar to production process, the role of alloying elements is also very important. Even minor changes in their compositions can cause significant changes in the final product. Simultaneously, these alloying elements appear to be more efficient in the development of new methods to control product quality, suppress defect formation, and improve material properties such as the creep and fatigue. As a result, the effects of various alloying elements used in castings of Ni-based superalloys are thoroughly examined. A material’s properties are its most important components. They assist the industrialist in selecting or developing a material based on the needs of the application/use. With this in mind, many researchers have conducted extensive research on physical and mechanical properties, as well as how to improve them. Fatigue life, stress rupture, creep properties, impact ductility, strain response, stress relaxation behaviour, and so on are some of the most important physical and mechanical properties of Ni-superalloys. This article thoroughly reviews various studies on these properties, how and by what factors they are affected, and how they can be improved. Another important factor to consider when making Ni-superalloy castings is defect formation, which can affect the properties of the final product. Freckle defects, hot tears, porosities, and slivers are some of the major defects that occur in Ni-superalloys during the casting process. This article also reviews in detail about these defects, how they form, and how they affect the final product. These defects were found to have a significant influence on a variety of properties, such as creep, fatigue behaviour, and fracture mechanism. Topics and areas such as reinforcement of Ni-superalloys with the help of CNCs and 3D printing of Ni-superalloys that can provide scope for potential future research are highlighted based on the above-reviewed papers.

Dissimilar Welding of Austenitic and Martensitic Stainless Steel Joints are commonly preferred in Nuclear Reactors where high temperature applications are needed. There has been a huge demand for materials which sustain corrosive environment with high rupture strength along with high temperature and pressure. These materials can be directly replaced with the traditional nickel based alloys to compensate for cost cutting and satisfy strength requirements. Dissimilar welding of these materials has been challenging due to the difference in its composition, properties and also heterogeneity in microstructure of these materials. A Study was done to identify what are the commonly used joining techniques, the mechanical properties of the joints and also the microstructure evolution of the dissimilar weld joints. This paper will emphasize on the work that was previously published in the area of dissimilar welding of these combinations of materials and also their challenges.

In this work, we report enhanced photocatalytic and magnetisation effects of nickel (Ni) ion doped titanium dioxide (TiO 2 ) nano particles. The nano crystalline TiO 2 doped with different concentrations of Ni (0.05-0.2%) were prepared by sol-gel method and characterised by various analytical techniques such as X-ray diffraction (XRD), UV-Vis spectroscopy, scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The Ni metal ions incorporation modified the microstructure of TiO 2 nano particles considerably which are evident from XRD and SEM analyses. The band gap reduction made by the Ni impurity level extends the TiO 2 optical absorption edge to visible region. The photocatalytic activity of TiO 2 and Ni-TiO 2 was studied by photo degradation of methyl orange dye as a function of irradiation time under visible light. The results signify that TiO 2 nanoparticles doped with the higher of concentration of 0.2% Ni improves the reaction rate of hydroxyl radical production. The electrochemical behaviour of the prepared samples was analysed by cyclic voltammetry study. The existence of hard ferromagnetic