Effect of laser shock processing on fatigue crack growth of duplex stainless steel

Duplex stainless steels have wide application in different fields like the ship, petrochemical and chemical industries that is due to their high strength and excellent toughness properties as well as their high corrosion resistance. In this work an investigation is performed to evaluate the effect of laser shock processing on some mechanical properties of 2205 duplex stainless steel. Laser shock processing (LSP) or laser shock peening is a new technique for strengthening metals. This process induces a compressive residual stress field which increases fatigue crack initiation life and reduces fatigue crack growth rate. A convergent lens is used to deliver 2.5J, 8ns laser pulses by a Q-switched Nd:YAG laser, operating at 10Hz with infrared (1064nm) radiation. The pulses are focused to a diameter of 1.5mm. Effect of pulse density in the residual stress field is evaluated. Residual stress distribution as a function of depth is determined by the contour method. It is observed that the higher the pulse density the greater the compressive residual stress. Pulse densities of 900, 1600 and 2500pul/cm2 are used. Pre-cracked compact tension specimens were subjected to LSP process and then tested under cyclic loading with R=0.1. Fatigue crack growth rate is determined and the effect of LSP process parameters is evaluated. In addition fracture toughness is determined in specimens with and without LSP treatment. It is observed that LSP reduces fatigue crack growth and increases fracture toughness if this steel. © 2010 Elsevier B.V

Laser Shock Processing of 6061-T6 Al alloy with 1064 nm and 532 nm wavelengths

Laser Shock Processing (LSP) has been proposed as a competitive alternative technology to classical treatments for improving fatigue and wear resistance of metals. We present a configuration and results in the LSP concept for metal surface treatments in underwater laser irradiation at 532 nm and 1064 nm. The purpose of the work is to compare the effect of both wavelengths on the same material. A convergent lens is used to deliver 1.2 J/pulse (1064 nm) and 0.9 J/pulse (532 nm) in a 8 ns laser FWHM pulse produced by 10 Hz Q-switched Nd:YAG laser with spots of a 1.5 mm in diameter moving forward along the work piece. A LSP configuration with experimental results using a pulse density of 2500 pulses/cm2 and 5000 pulses/cm2 in 6061-T6 aluminum samples are presented. High level compressive residual stresses are produced using both wavelengths. It has been shown that surface residual stress level is comparable to that achieved by conventional shot peening, but with greater depths. This method can be applied to surface treatment of final metal products. 2010 Elsevier B.V. All rights reserved

Application of laser shock processing system by underwater irradiation (1064 nm) in metal surface

Laser shock processing (LSP) is a technique for strengthening metals. This process induces a compressive residual stress field which increases fatigue crack initiation life, reduces fatigue crack growth rate and increases wear resistance of metals. We present a configuration and results in the LSP concept for metal surfaces treatments in underwater layer with constant thickness using laser irradiation at 1064 nm. A convergent lens is used to deliver 2, 5 J/cm2 in a 8 ns laser FWHM pulse produced by a Q-switch Nd:YAG Laser. Experimental results using a pulse density of 5 000 pulses/cm2 and spots of 0, 8 mm to 1, 5 mm in diameter on AISI 1040 steel surfaces, Ti6Al4V surfaces, 304 Stainless Steel surface and 6061-T6 Aluminum surfaces are presented. A compressive residual stress distribution as a function of depth is assessed by the hole drilling method. High level compressive residual stresses are produced using a 1064 nm wavelength. This method can be applied for surface treatment of final metal products. Zapotitlán 2008 American Institute of Physics

Laser shock processing to improve residual stresses with and without paint layer on 6061-T6 aluminum alloy

Laser shock processing (LSP) or laser shock peening has been proposed as a competitive alternative technology to classical treatments for improving fatigue and wear resistance of metals. This process induces a compressive residual stress field which increases fatigue crack initiation life and reduce fatigue crack growth rate. We present a configuration and results in the LSP concept for metal surface treatments in underwater laser irradiation at 1064 nm with and without a thin surface paint layer. A convergent lens is used to deliver 1, 2 J/cm2 with a 8 ns laser FWHM pulse produced by a 10 Hz, Q-switched Nd-.YAG laser with a spot diameter of a 1,5 mm moving forward along the workpiece. A LSP configuration with experimental results using a pulse density of 5 000 pulses/cm2 in 6061-T6 aluminum samples are presented