A method of forming a thermally insulating layer system on a metallic substrate surface is disclosed. The method includes: forming a plasma beam; introducing a coating material in the form of a powder having particles in the range between 1 and 50 μm, carried by a delivery gas into the plasma beam, so as to form a powder beam; defocusing the powder beam by using the plasma beam with a sufficiently high specific enthalpy and by maintaining a process pressure between 50 and 2000 Pa for at least partially melting and vaporizing at least 5% by weight of the powder, so as to form a vapor phase cloud; and forming from the vapor phase cloud onto the metallic substrate surface an insulating layer, being a part of the insulating layer system, having an anisotropic columnar microstructure having elongate particles; wherein the anisotropic columnar microstructure is aligned substantially perpendicular to the metallic substrate surface and low-density transition regions with little material delimit the elongate particles relative to one another.