Microstructure and properties of a Ti doped Fe-based SMA coating produced by laser cladding

Abstract

To improve the microhardness and wear resistance of Fe-based shape memory alloy (SMA), a Ti doped Fe-based SMA coating was prepared on 304 stainless steel by laser cladding. The phase transition temperature, microstructure, phase composition, microhardness, wear and corrosion resistance of the coating were investigated by differential scanning calorimeter, scanning electron microscopy, X-ray diffractometer, microhardness tester, friction tester and electrochemical workstation respectively. The ε → γ phase transition temperature As and Af of the composite coating are 467 and 475 °C, respectively. Furthermore, it has a shape recovery rate of 30.98% at a deformation of 8.4%. The coating has stress self-accommodation characteristics and shape memory effect. There are TiC, γ-austenite and ε martensite phase in the SMA + Ti coating. The average microhardness of the SMA + Ti coating is 1/3 higher than that of the SMA coating, and up to 1/2 compared to the substrate. The friction coefficient of the SMA + Ti coating is 1/3 smaller than that of the SMA coating, and 1/2 compared to the substrate. Corrosion resistance of the SMA + Ti coating has been improved.

Keywords

• Laser cladding
• Shape memory alloy
• Strengthening
• Microstructure
• Wear resistance