In situ strategy towards enhancing cold spray coating deposition efficiency

Cold spray is an advanced surface engineering technique for producing dense coatings with high adhesion; however, its deposition efficiency is often limited by the thermal and kinetic parameters of the process. This study proposes an in situ strategy to enhance deposition efficiency by redesigning the gas heating system of a low-pressure cold spray (LPCS) machine DIMET-405. A novel heater with increased power (5.3 kW versus the standard 3.3 kW) was developed and tested to compensate for the temperature drop associated with higher gas stagnation pressures. Experimental results showed that the new gas heater enabled stable gas heating to 605 °C at an inlet pressure of 1.0 MPa, compared to only 373 °C achieved with the standard configuration. This improvement significantly increased the velocity and temperature of powder particles in the nozzle flow, leading to enhanced particle deformation and adhesion upon impact. As a result, the thickness of aluminum coatings deposited on titanium substrates increased more than fivefold under identical spraying conditions. Moreover, deposition efficiency rose from 13.4% with the standard heater to 60.6% with the developed heater. Microstructural analysis confirmed the formation of dense, homogeneous coatings with strong interfacial bonding and reduced porosity. The findings highlight the critical role of inlet gas temperature in controlling the quality of cold spray coatings, demonstrating that relatively simple in situ modifications to the heating system can substantially improve both the effectiveness and reliability of the process. This approach offers a practical pathway for optimizing cold spray technology in aerospace and related applications that require high-quality, defect-free coatings.