Compression fatigue behavior of Fe-C-Cr-Nb alloys surfaced on 45 steel

The compression fatigue behavior of six kinds of Fe-C-Cr-Nb surfacing alloys on the base metal of 45 steel was tested with self-designed dual-notch fatigue specimens according to the compression fatigue working condition of the cement squeeze roller. In-situ observation and laser confocal crack analyses were carried out on the surface of fatigue specimens. The stress-strain concentration of the notches accelerated the accumulation of slip lines at local HAZ just below the notches and plastic deformation zones formed there. At the same time, fatigue cracks were initiated at the bottom edge of the notches and propagated into HAZ through surfacing alloys. Fatigue cracks were initiated and propagated along the fusion line as well and eventually resulted in fatigue failure. The experimental results show that the a-N curves of fatigue specimens were approximately straight lines. When the matrix micro-structures of the surfacing alloys were mainly composed of martensite with high hardness, the fatigue crack propagation rate is big and the fatigue life is only 50,000 times. While the micro-structures were composed of soft ferrite or austenite, the propagation rate is small and the fatigue life is up to 540,000 times.