Laser shock processing for improving fatigue property of K403 cast superalloy

The high-energy Nd: YAG laser YLSS-M60U was adopted for laser shock processing on K403/K3 cast superalloy test specimen from pressure-turbine blade materials of a certain type of engine. The processing parameters are: laser energy 3 J, spot diameter 2.6 mm, laser pulse 20 ns, laser wave length 1064 nm. An aluminium foil was used as the protection coating, along with water as the restraint layer, the overlap rate reached 50% after 3 times of shocking. The high-cycle fatigue (HCF) test was conducted under the room temperature at stress level of 420 MPa as well as the SEM observation and XRD (x-Ray diffraction) analysis after laser shock processing. The study shows that the leading reasons for improving the fatigue property of metal involve that the fatigue life of the test specimen was 2.4 times longer than the original after laser shock processing, the strong shock waves plastically deform the metal with high-strain rate and generate much larger and deeper residual compressive stress.