Residual Stress Analysis of Boronized AISI 1018 Steel by Synchrotron Radiation

AISI 1018 steel substrates were powder-pack, diffusion boronized at 850 °C for 4 h, followed by air quenching. Optical microscopy in conjunction with color etching was used to obtain the average penetration depth of the iron monoboride layer (9 μm) and the iron diboride layer (57 μm). X-ray diffraction by synchrotron radiation, conducted at the National Synchrotron Light Source in Brookhaven National Laboratory, confirmed the presence of iron monoboride and iron diboride in the boronized plain steel substrates. The sin² ψ technique was employed to calculate the residual stress found in the iron monoboride layer (−237 MPa) and in the substrate layer (−150 MPa) that is intertwined with the needle-like, iron diboride penetration.