A statistical study of the Spraying Xplorer AMT system was undertaken in order to check that if it can be used as a means of assistance for on-line production control. A patented procedure of the system calibration is explained and some results are presented.

The development of High Velocity Oxy-Fuel (HVOF) process shows a clear trend toward the design of new gun in which high pressure and large power are expected in order to obtain a stable flame and a high powder feed rate for industrial applications. In this work, a new HVOF gun, AMT-200, was used to prepare NiCrAlY and WC-Co-Cr coatings. To optimise the spraying parameters, i.e., flux rates of oxygen and fuel gas and spraying distance, the on line control system AMT Spraying Xplorer was used. The results show that the spraying parameters play significant roles on the properties of NiCrAlY coatings. Employing optimized parameters, a dense NiCrAlY coating, with a high coating/substrate bonding strength and low oxygen content, could be obtained by this system. Moreover, thermal treatment could reduce significantly the coating porosity and increase greatly coating/substrate bonding strength. The preliminary tests on WC-Co-Cr coating indicate that dense cermet based coatings could be deposited with this system.

The aim of this work is to produce titanium dioxide coatings doped with silicon dioxide nanoparticles. Nanoscale SiO 2 powders are prepared in an induction plasma reactor, then spray-dried to obtain a homogeneous mixture of micro- and nano-crystalline oxide powders suitable for dc plasma spraying. A test case based on conventional aluminum oxide powder is presented. Paper includes a German-language abstract.

In general, thermal spraying involves high temperatures that can be deleterious for the microstructure and deformation of the substrate. As a consequence, the use of a cooling system during spraying is often necessary. Meanwhile, in some cases, a too low surface temperature can induce a loss of properties, in particular concerning adherence and coating density. Therefore, it would be sometimes interesting to combine pre-heating and cooling stages with the plasma spray. A specific process, named HeatCool, was developed and patented to ensure a precise control of the temperature at the spraying location. The present work was focused on the study of the influence of pre-heating and cryogenic cooling conditions on the microstructure and mechanical characteristics of NiCrFeBSi self-fluxing alloy deposited by d.c. plasma spray technique. Firstly, a comparison between air and CO2 cooling was conducted to assess the efficiency corresponding to the specific use of cryogenic CO2. The main characteristics studied were the microhardness, roughness, porosity, mechanical deformations, morphology and crystallographic structures. Optimising the cooling methods and conditions combined with the process parameters improved microhardness of the plasma sprayed metal alloy and induced lower strain deformation of the substrate. Secondly, the pre-heating system was added to the device and the HeatCool process was evaluated. The process was demonstrated to be an efficient mean to enhance the structural and mechanical characteristics of coatings made of self-fluxing alloy.