Preparation and thermal shock performance of thick α-Ta coatings by direct current magnetron sputtering (DCMS)

Thick α-Ta coatings were fabricated on 30CrNi3MoV steel by DCMS process. The specimens were located at the negative glow space between the cathode and anode, where the temperature of the sample surface will be heated up across the temperature of β → α transformation zone within several minutes, by impacting the specimens frequently with large kinetic and electrical energy of the electrons. Thick α-Ta coating exhibits good thermal shock resistance. The coefficient of thermal expansion (CTE) mismatch among interfaces caused large residual stress of Ta coating during the thermal cycles, and is the main factor of coating failure.