Effect of pressure on microstructure and properties of Ti–Al coating on titanium alloy surface

Abstract

The effect of pressure on the microstructure and properties of Ti–Al coating on titanium alloy surface is studied. Ti–Al coating is prepared on the surface of titanium alloy by pressure-assisted high-temperature thermal diffusion. The manufacturing method is simple and easy to operate. The microstructure and element distribution of the coating are analyzed under different processes, and the composition of the coating is tested. The test results show that the substrate alloy and the coating alloy are not connected when the coating is diffused at 650 °C. The coating diffused at 750 °C without pressure is mostly connected to the substrate, but there are microscopic gaps in some areas. The main components of the coating diffused at 750 °C under 80 Pa pressure are TiAl, Ti3Al, and other intermetallic compounds. The boundary between the substrate and the coating is flat, and there is no obvious micro gap, so the metallurgical connection is fundamentally realized. In addition, the maximum hardness can reach 334.9HV0.2. The thickness of the coating diffused at 750 °C under 160 Pa pressure was greatly reduced, showing a gradient form. The surface quality of the outer coating is poor, the structure density of the binding layer is also poor, and there are no obvious penetrating cracks. The bonding between the coating and the substrate is effectively enhanced by an auxiliary action under certain pressure, and then the microstructure and properties of the coating are improved.