Post treatment of cold sprayed coatings using high-energy infrared radiation: First comprehensive study on structure-property correlation

Abstract

It is a well-known fact that cold sprayed coatings need post treatment to achieve properties close to their bulk counterparts even when the coatings are obtained using high pressure cold spray. Most often post treatments are conventional furnace heat treatments primarily to relieve stresses and improve splat bonding. However, this methodology cannot be used all the time given the dimensional constraints of a furnace. Use of in tandem heating or mobile heating tools can greatly enhance the commercial potential of cold spray provided the heating tools are cheaper and easily available. In the present study, one such heating tool viz., high energy infrared emitters are used to post treat cold sprayed copper based coatings. A comprehensive study exploring the influence of heating power density and exposure duration on coating properties and microstructure has been taken up in the present work. Furnace heat treatment studies and post treatment of CuAl alloy coatings has also been studied for comparison. Pure Cu coatings respond exceedingly well to the mobile post treatment in terms of amelioration in coating microstructure and properties comparable to and better than furnace. An analysis of the contribution from different microstructural features to the coating properties especially electrical conductivity have been made. In contrast, CuAl alloy coatings respond less favourably to both infrared and furnace post treatments. A discussion towards this anomalous behavior is also provided with the help of the microstructural observations.