Chemistry and microstructure of PLD (Ti, Al) C_xN_1-x coatings deposited at room temperature

The aim of the present work was the improvement of titanium-aluminium nitride (TiAlN) coatings by the solid-solution hardening with carbon atoms leading to titanium-aluminium carbon-nitride (Ti, Al) C_xN_1-x coatings with varying cabon (x) and nitrogen contents. The request of low deposition temperatures necessary for the coating of heat sensitive materials like tool steels of high hardness and polymer was reached by the application of the room temperature pulsed laser deposition (PLD) technique. A Nd:YAG laser of 1064nm wavelength operated at two different laser pulse energies was used in the ablation experiments of pure TiAl targets (50 at. % Al) in various C₂H₂-Ar gas mixtures. Different puls energies of the laser resulted in changes of the ratio of Ti/Al atoms in the grown coatings. Furthermore, the resultes reveal a strong proportinality of the gas mixture to the C and N content of the coatings. In the coatings deposited at low C₂H₂ gas flows the XRD investigations showed crystalline phases with fcc TiN type lattice, whereas high acetylene flows during deposition resulted in the formation of fully amorphous coatings and carbon precipitation or cluster boundaries found in Raman investigations.