Effect of energy distribution on laser cleaning quality of 30Cr3 ultra-high strength steel

Abstract

30Cr3 is a novel ultra-high strength steel (UHSS) with excellent strength and plastic toughness, which has been mainly used in aerospace shells and stressed parts. Currently, there is still a lack of systematic research and comprehensive evaluation on the laser cleaning of this particular material. In this study, a nanosecond pulsed laser was employed for the cleaning process. First, the energy distribution model was derived, the influence of the spatial and temporal distribution of laser energy on the cleaning quality was discussed, and the cleaning experiment was conducted. The results showed that a laser energy density of 15 J/cm2, combined with the beam overlap rate 52% in the x-direction and 61% in the y-direction, can effectively remove the oxide layer and thoroughly expose the natural metal matrix. Then, under the optimum parameters, the oxygen content decreased from 22.3% to 3.4%, the Fe content increased from 54.5 to 83.4%, the Fe3+ peak disappeared in the X-ray photoelectron spectroscopy (XPS), a remelted layer of only 1 μm was observed. Last, the roughness was slightly reduced from 3.573 μm to 2.985 μm, the hardness was restored to the original hardness level of the substrate (∼260 HV), and the electron back scatter diffraction (EBSD) showed that the structure hardly changed after cleaning, the grain size was comparable to that of the matrix. These findings indicated that laser cleaning can effectively remove the oxide layer of 30Cr3 UHSS without damaging the properties of the base material, which has promising application in the cleaning of UHSS.