Since the first thermal spraying process for feeding tin and lead wires into a modified oxyacetylene welding torch patented by M. U. Schoop (Zurich, Switzerland) between 1882 and 1889, thermal spray technology has been continuously developed to meet market requirements. It has evolved into a large family of processes that now includes flame spray, electric arc spray, plasma arc spray, and more recently the high kinetic energy spraying known as cold spray.

Over the past 25 years, a significant trend has been to increase the velocity of the sprayed material to get denser and harder coatings and limit possible oxidation and material transformation. This has led to a search for lower temperature processing methods and technologies such as “cold spray” and “warm spray.” During the same period, a lot of research has been carried out on all thermal spray processes on controlling the microstructure and properties of coatings and improving their performance and reproducibility.

In the 1990s, there was the boom of nanomaterials that quickly spread out in the thermal spray community and led to the development of spraying liquid feedstocks, in the form of suspensions or solutions, and the spraying of particles made by agglomeration of nanoparticles. Also, the technology took advantage of the high enthalpy content of the gas jet, in particular plasma jets, for evaporating the spray material and forming coatings by the condensation of the vaporized material on the substrate. The spraying of liquid feedstocks, and also the formation of coatings from the vapor phase, have allowed the formation of “thin” coatings and thus broadened the range of coating thickness attainable by thermal spray processes. These developments close the gap between deposition techniques that were traditionally classified as “thick coatings “and “thin coatings” technologies.

In thermal spraying, innovations are concerned not only with process improvements but also with finding suitable materials for more demanding and challenging applications. New needs and applications are still emerging, providing a rich source of challenging topics for researchers and engineers working in that field.

The purpose of this special issue is to highlight the most recent advances in thermal spray technologies. It includes six comprehensive reviews dedicated to process development and 23 articles submitted in response to the call for this special issue. The invited review contributions deal with warm spray technology, suspension and solution precursor thermal spray processes, flame-based technologies and reactive spray deposition technology for low temperature solid oxide fuel cell, laser processes used in combination with thermal spray technologies, plasma spray-PVD, and nonequilibrium atmospheric plasma deposition techniques.

The open call for contributions for this issue received a very strong response as more than 100 abstracts were sent to the journal. Therefore, a first selection of abstracts had to be done. This response shows the intense activity and strong interest of the thermal spray community in the ongoing development and applications of this technology.

The series of papers published in this special issue may not cover this subject in its entirety and potential contributions on other equally exciting subjects may be missing. However, we expect that this issue will provide an extensive view of current developments in thermal spraying and promote new research that will further expand the applications and markets of thermal spraying. In closing, we would like to thank all the authors who submitted abstracts and papers and the nearly 60 reviewers who provided high-quality and diligent reviews.