Click on the title to browse this book

One of the main specific features of the cold spray process is localisation during particle impact deformation. The resultant adiabatic shear instability is the phenomenon that is known to play a major role in the particle/substrate and particle/particle bonding and coating structure formation during the cold spray process. In this article, the cold spray process is numerically simulated as an impact between a single spherical particle with the substrate, and comparison with experimental results for Armco iron and stainless steel particles is made. To describe a deformation behavior of the two materials at high strain rates, the Johnson–Cook model has been chosen. The results indicate that the model accurately captures the grain distortion in the impact zone for both materials. This approach provides valuable information on the characterisation of the strain localisation at the particle/substrate interface.

Hydroxyapatite is a widely used material used for the bioactivation of an implant’s surface. A promising hydroxyapatite coating approach is the kinetic deposition of powder particles. The possibility of solid-state deposition improvement through the merging of Aerosol Deposition and Low Pressure Cold Spraying techniques is a promising prospect for improving the deposition efficiency and the quality of coatings. The objective of the paper is to study the possibilities of hydroxyapatite coating structure modification through changes in the coating process and post-heat treatment. The novel Aerosol Cold Spraying system joining Low Pressure Cold Spraying and Aerosol Deposition was used for the deposition of coatings. The coating’s post-processing was conducted using two techniques: Spark Plasma Sintering and Pressureless Sintering. The coating’s structure was examined using scanning, transmission, and light microscopy, and X-ray diffraction. Substrate–coating bond strength was assessed using a tensile test. Homogenous buildup using Aerosol Cold Spraying of hydroxyapatite was achieved. Various pores and microcracks were visible in the sprayed coatings. The deposition process and the thermal post-processing did not lead to significant degradation of the hydroxyapatite phase. As a result of the Spark Plasma Sintering and Pressureless Sintering at 800 °C, an increase in tensile adhesion bond strength and crystal size was obtained.