Improvement of surface hardness of duplex stainless steel by laser shock hardening for the application to seawater desalination pump

Abstract

A high-capacity pump for seawater desalination plant is open to highly corrosive and abrasive environment. To improve anti-corrosion and anti-abrasion properties of pump material, laser modification technology can be applied to the surface of pump material. In this work, experimental results for the laser shock hardening of 2205 duplex stainless steel (22% chromium-5% nickel) for the application to rotating pump parts are reported. The changes in surface hardness and morphology before and after laser shock hardening are investigated for varying process conditions. It is demonstrated that the hardness of duplex stainless steel can be significantly enhanced, up to 30%, by properly controlling the process parameters. The applicability of laser shock hardening for surface treatment of mechanical parts of seawater desalination pumps is discussed.

Laser Shock Peening of Duplex Stainless Steel in Comparison with Other Methods of Surface Treatment

“…Almost the same hardening depth was obtained by water immersion type LSP. 20,21 In contrast, the hardening depth achieved by SP was merely about 0.2~0.3 mm. 12,14 As shown in Fig.…”

“…2, the degree of surface hardness increase achieved by various surface treatment methods is presented. Previously, we reported 20,21 that the maximum increase of surface hardness achieved by water immersion type LSP was about 29% (optimum conditions: Nd: YAG laser, wavelength = 532 nm, pulse duration = 8 ns, ß at top proÞ le, laser irradiance = 10 GW/cm 2 , spot diameter = 1.5 mm, pulse density = 75 pulse/ mm 2 , protective coating = 100 m Al foil). With the nozzle type LSP (using the same laser), we obtained about 25% enhancement in Vickers hardness (Akashi, HM-112, 1 kg load for 10 s) at the conditions of laser irradiance = 10 GW/cm 2 , spot diameter = 1.2 mm, pulse density = 10 pulse/mm 2 , protective coating = 100 m Al foil.…”

“…The authors reported the enhancement of surface hardness, wear resistance, and corrosion resistance of 2205 DSS by water immersion type LSP. 20,21 Rubio-Gonzalez et al 22 investigated the effects of LSP on fatigue crack growth of DSS. These recent studies for LSP of DSS demonstrated that LSP could be an effective method to achieve a simultaneous improvement of hardness, wear resistance, and corrosion resistance of DSS.…”