Impact fracture and residual stress analysis of 2Cr13 steam turbine blades after laser alloying

摘要

As a key part in steam turbine,the surface hardness,fatigue strength capacity and corrosion resistance of the turbine blades are the major concerns. 2Cr13 is a commonly used material on steam turbine blades due to its fine mechanical properties,high anti-fatigue and good weldability. However,under the impact of high-speed steam and water droplet,cavitation is prone to form on the blades,which could lead to lower efficiency,shorter life time,and even accidents. In order to improve the cavitation resistance of steam turbine blades (low-carbon martenstic stainless steel,2Cr13),7K W continuous wave CO2 laser processing system is used for surface alloying. The microstructures,microhardness,fracture pattern and residual stress of laser alloying layer are studied by X-ray residual stress tester,scanning electronic microscope (SEM),X-ray diffraction (XRD),energy disperse spectroscopy (EDS),and microhardness tester. After laser alloying,the surface present high residual compression and the HAZ present low residual tensile stress. The microstructure of surface is refined after laser alloying which is different from the substrate. The average microhardness after laser alloying is 701.2 HV0.2 (while base materials 200-250HV0.2).The fracture pattern is analyzed as well.