In this work, modelling of Nitinol (Ni-45 wt.%Ti) coating deposition, by means of High Velocity Oxygen-Fuel (HVOF) technology, is presented. Species transport model and the k-ϵ turbulence model were solved in Ansys Fluent environment, in which combustion between kerosene and oxygen, gas and particle flow in a GTV HVOF-K2 gun (GTV Verschleiss-Schutz GmbH, Germany) were simulated. The effect of spraying process parameters, such as spray distance, particle shape factor, and kerosene to oxygen feed rate ratio, affecting coating properties and quality, on the supersonic gas flow dynamics, particle velocity and temperature, was numerically investigated. Moreover, correlation between modelling findings and coating quality was explored. Numerical findings highlighted that the higher the kerosene to oxygen feed rate ratio the higher the temperatures and velocities of both gas and particles and the combustion pressure; moreover, with particle shape factor lower than 1, velocity of particles increased while ultimate temperature decreased. Furthermore, the findings of this study allowed to predict the properties of impacting Nitinol particles on substrates and showed the thermal story of the particle from the injection to the impact. These above-mentioned aspects are of great importance because Nitinol is a Shape Memory Alloy and its performances strongly depend on stress and thermal state.
Modeling of hvof thermal spray deposition of nitinol coating: Effect of spraying process parameters on gas and particles properties and coating quality
Chianese, Simeone;Musmarra, Dino
2018
Abstract
In this work, modelling of Nitinol (Ni-45 wt.%Ti) coating deposition, by means of High Velocity Oxygen-Fuel (HVOF) technology, is presented. Species transport model and the k-ϵ turbulence model were solved in Ansys Fluent environment, in which combustion between kerosene and oxygen, gas and particle flow in a GTV HVOF-K2 gun (GTV Verschleiss-Schutz GmbH, Germany) were simulated. The effect of spraying process parameters, such as spray distance, particle shape factor, and kerosene to oxygen feed rate ratio, affecting coating properties and quality, on the supersonic gas flow dynamics, particle velocity and temperature, was numerically investigated. Moreover, correlation between modelling findings and coating quality was explored. Numerical findings highlighted that the higher the kerosene to oxygen feed rate ratio the higher the temperatures and velocities of both gas and particles and the combustion pressure; moreover, with particle shape factor lower than 1, velocity of particles increased while ultimate temperature decreased. Furthermore, the findings of this study allowed to predict the properties of impacting Nitinol particles on substrates and showed the thermal story of the particle from the injection to the impact. These above-mentioned aspects are of great importance because Nitinol is a Shape Memory Alloy and its performances strongly depend on stress and thermal state.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
