Ti 2AlC coatings deposited by High Velocity Oxy-Fuel spraying

Abstract

High Velocity Oxy-Fuel has been utilized to spray coatings from Ti 2AlC ( MAXTHAL 211 ®) powders. X-ray diffraction showed that the coatings consist predominantly of Ti 2AlC with inclusions of the phases Ti 3AlC 2, TiC, and Al–Ti alloys. The fraction of Ti 2AlC in coatings sprayed with a powder size of 38 μm was found to increase with decreasing power of the spraying flame as controlled by the total gas flow of H 2 and O 2. A more coarse powder (56 μm) is less sensitive to the total gas flow and retains higher volume fraction of MAX-phase in the coatings, however, at the expense of increasing porosity. X-ray pole figure measurements showed a preferred crystal orientation in the coatings with the Ti 2AlC (000 l) planes aligned to the substrate surface. Bending tests show a good adhesion to stainless steel substrates and indentation yields a hardness of 3–5 GPa for the coatings sprayed with a powder size of 38 μm.