Effect of laser cladding speed on microstructure and properties of titanium alloy coating on low carbon steel

Abstract

Titanium and its alloys have excellent corrosion resistance in the marine environment, but their applications are limited by the high cost of raw materials and manufacturing difficulties. In this work, we successfully prepared a thin titanium alloy coating on the low carbon steel surface by a laser cladding method. With a systematical study on the cladding process, the laser cladding speed is found to be the crucial parameter to tune the coating performance. On the one hand, the corrosion resistance is determined by the laser cladding speed. The higher laser cladding speed leads to a thinner coating thickness, and the melted titanium powder is less resulting in a high dilution rate. The increase of the dilution rate is more likely to cause surface cracks, and the corrosion resistance decreases due to these cracks and the formation of the Fe-Ti intermetallic compounds on the coating surface. When the laser cladding speed is 6 mm/s, the sample possesses the lowest dilution rate of 9.9 % and the best corrosion resistance (Ecorr of −0.247 V and Icorr of 1.526 × 10−8 A·cm−2). Therefore, the critical dilution rate D (9.9 %) can be proposed as the optimization goal for the laser cladding speed. When the dilution rate is equal to or lower than the D, the corresponding laser cladding process can guarantee sufficient corrosion resistance of the titanium alloy coating. On the other hand, the laser cladding speed can also influence the coating hardness and the interfacial adhesion strength between the coating and substrate. When the laser cladding speed is slow, the coating hardness decreases to a certain extent, while the interfacial adhesion strength slightly descends. Therefore, this work can expedite the effective applications of titanium alloys in marine engineering equipment, with a greatly reduced cost and ensured performance.