COLD SPRAY ADDITIVE MANUFACTURING

Abstract

Cold spray additive manufacturing (CSAM) is a recent member of the large thermal spray family and has quickly become a promising solid-state additive manufacturing technology. In the CSAM process, micron-sized (5-50 µm) powder particles are fed into a stream of preheated (up to 1100°C) and pressurized (up to 7 MPa) propellant gas (usually nitrogen or helium) and are accelerated to ultrahigh velocities (300-1500 m/s). The highly kinetic in-flight particles are then impacted on the substrate, where they plastically deform, realign, and finally adhere to form high-quality deposits. Due to the solid-state deposition characteristics, CSAM can exhibit many advantageous features such as high deposition rate (>30 kg/h), wide materials selection (metals, alloys, mixtures), unlimited workpiece size/deposit thickness, low oxidation content, high performance of the deposit (density and strength). CSAM has undergone rapid development in the recent years and attentions from both academia and industry are growing exponentially. CSAM has found its niche markets in additive manufacturing industry such as fabricating large-scale 3D metal components with relatively simple geometries. In this chapter, we mainly sum up the state-of-the-art knowledge of CSAM in the following four sections. In the first section, the brief history and technology characteristics of CSAM are introduced. In the second section, the types of common sprayable materials used in CSAM are listed. The four important engineering materials, i.e., Cu alloys, Al alloys, Ti alloys, Ni superalloys, are also discussed in detail regarding to their sprayability, deposit microstructures, and properties in CSAM. In addition, typical implementation statuses of CSAM in different industry domains are presented, including repair & remanufacture, biomedical, electronics & semiconductors, power & energy, aerospace & astronautics. In the third section, we see the introduction of the main process parameters in CSAM and the respective roles, together with the key process control methods in CSAM, including the nozzle, the spray track simulation strategy, closed loop control and online monitoring, and deep learning for CSAM shape control. In the final section, a short conclusion is drawn, and the current challenges and future perspectives of CSAM are also summarized in this section. In general, although CSAM is still at the initial stages of application, it has exhibited significant advantages in many industry domains, such as rapid/mass production, manufacturing, and repair of high value engineering parts. Global awareness of current and future CSAM activities is essential to expanding their implementations and benefits.