Wire Arc Additive Manufactured Mild Steel and Austenitic Stainless Steel Components: Microstructure, Mechanical Properties and Residual Stresses.

Wire arc additive manufacturing (WAAM) is an additive manufacturing process based on the arc welding process in which wire is melted by an electric arc and deposited layer by layer. Due to the cost and rate benefits over powder-based additive manufacturing technologies and other alternative heat sources such as laser and electron beams, the process is currently receiving much attention in the industrial production sector. The gas metal arc welded (GMAW) based WAAM process provides a higher deposition rate than other methods, making it suitable for additive manufacturing. The fabrication of mild steel (G3Si1), austenitic stainless steel (SS304), and a bimetallic sample of both materials were completed successfully using the GMAW based WAAM process. The microstructure characterization of the developed sample was conducted using optical and scanning electron microscopes. The interface reveals two discrete zones of mild steel and SS304 deposits without any weld defects. The hardness profile indicates a drastic increase in hardness near the interface, which is attributed to chromium migration from the SS304. The toughness of the sample was tested based on the Charpy Impact (ASTM D6110) test. The test reveals isotropy in both directions. The tensile strength of samples deposited by the WAAM technique measured slightly higher than the standard values of weld filament. The deep hole drilling (DHD) method was used to measure the residual stresses, and it was determined that the stresses are compressive in the mild steel portion and tensile in austenitic stainless steel portion, and that they vary throughout the thickness due to variation in the cooling rate at the inner and outer surfaces.

Experimental investigations on viscosity and density of eco-friendly MoS2-sesame oil nano-lubricants and its influence on pumping power.

In this study, the rheological behavior and density of MoS2/sesame oil based nano-lubricants are experimentally investigated. The transmission electron microscopy and x-ray diffraction technique were utilized to confirm the morphology of the MoS2nano particles. The experimental measurements are carried out at temperature varying from 313 to 393 K, shear rate ranging from 10to 70 s-1and solid volume fraction ranging from 0.2% to 1.2%. For the both nano-lubricants and pure lubricant, shear thinning behavior is observed. The influence of temperature and nanoparticle concentration on viscosity and density of nano lubricants are examined. The viscosity and density of nano-lubricants increased with an increase of solid volume fraction, while, it decreased with an increase in temperature. Moreover, the effect of nano particle concentration on the pumping power of lubricant flow are discussed. Finally, an experimental correlation was developed for predicting the viscosity of MoS2/sesame oil based nano-lubricant.