Bandar AlMangour

Fundamentals of Cold Spray Processing: Evolution and Future Perspectives

Cold gas dynamic spraying, or cold spraying (CS), is a solid-state coating process wherein powders in a carrier gas are accelerated toward a substrate. Under sufficiently high impact velocities, the powder particles deform plastically and adhere to the substrate. Metals, ceramics, polymers, and composites can be deposited using CS. Among currently available surface coating technologies, CS offers several advantages over thermal spraying, because it utilizes kinetic rather than thermal energy for deposition. This avoids residual stresses, oxidation, and undesirable chemical reactions. The intent to develop new material systems with enhanced properties that fulfill the required surface and interface functionalities for components with many applications has inspired CS investigations of many material combinations. The number of studies and patents on CS and CS-related technologies has increased exponentially in recent years, establishing much new information in a short time. In this chapter, the process of CS is discussed from mechanistic and technological perspectives, including its general operating parameters, current applications to specific material systems, and ongoing research increasing the scope of the technique. A critical discussion on developing CS technologies examines the microstructural bonding mechanisms utilized in variations on the process. Future investigations are suggested, particularly in quantitatively linking CS processing parameters to the behaviors of material systems during impact. This chapter briefly summarizes the rapidly expanding common knowledge on CS to assist researchers and engineers in future endeavors with this technology.

Effect of Stress Relieving Heat Treatment on the Microstructure and High-Temperature Compressive Deformation Behavior of Ti-6Al-4V Alloy Manufactured by Selective Laser Melting

This study aims to investigate the effect of stress relieving heat treatment on the microstructure and high-temperature compressive deformation behavior of the Ti-6Al-4V alloy, manufactured by selective laser melting. Initial microstructural observation confirmed elongated prior β grains in the building direction of both specimens (as-fabricated and heat-treated specimens). Along with such, the as-fabricated specimen only featured α′-martensite phase, while the heat-treated specimen featured α′-martensite and some α and β phases. Compression tests carried out at room temperature gave yield strengths of 1365 and 1138 MPa for the as-fabricated and heat-treated specimens, respectively. Such values are similar or greater than those of commercial wrought materials. The compressive fracture strain significantly increased after heat treatment. There was a general tendency of reducing yield strength as compressive temperatures increased. At temperatures greater than 700 °C, the as-fabricated and heat-treated specimens achieved similar strength. Microstructural observation after deformation confirmed that the initial microstructure was retained up to temperatures of 500 °C. At 700 °C or greater, both specimens showed drastic microstructural evolution.