Plasma spray apparatus and method

A thermal plasma spray method for coating substrates, comprising the steps of:

• providing at least a working chamber including at least a plasma torch and at least a substrate support for the substrate to be coated, in which an inert gas or a mixture of inert gases is contained at a pressure which is equal to, or higher than, atmospheric pressure,
• providing at least a gas circuit, in communication with said working chamber, comprising recirculating means of the inert gases contained in said working chamber,
• performing thermal plasma spray coating on the substrate using the plasma torch,
• said recirculating means comprising a closed loop, including a first heat exchanger and a recirculating blower arranged upstream of said first heat exchanger and communicating with said working chamber, said recirculating blower extracting the inert gas or the mixture of inert gases from said working chamber, and said heat exchanger cooling down the extracted inert gas or the mixture of inert gases,
• supplying a first fraction of recirculated and cooled inert gas or mixture of inert gases into a first gas inlet of the working chamber, and
• wherein said recirculating means further comprises a path communicating with said closed loop downstream of the first heat exchanger, said path including a second heat exchanger, and at least a compressor, arranged upstream of said second heat exchanger, said compressor compressing a second fraction of said recirculated and cooled inert gas or mixture of inert gases, and said second heat exchanger cooling down the compressed second fraction of inert gas or mixture of inert gases,
• supplying said second fraction of recirculated, compressed and further cooled inert gas or mixture of inert gases into a second gas inlet of said working chamber,
• wherein the second gas inlet communicates with one or more conduits in said working chamber, said one or more conduits pointing said second fraction of recirculated, compressed and further cooled inert gas or mixture of inert gases towards the substrate,
• wherein outlets of said one or more conduits comprise air amplifiers geometrically configured to increase the flow rate of gases or mixture of gases.