Enhanced wear resistance by combined ultrasonic impact and electro-spark melting

摘要

A novel surface modification method coupling surface melting and ultrasonic impact treatment (UIT) was developed to improve the wear resistance of S355 steel. The principle of ultrasonic impact electro-spark melting treatment (UIEMT) was presented, and the microstructure and surface plastic deformation layer were characterised by scanning electron microscopy, optical microscopy and X-ray diffraction (XRD). The obtained results revealed that UIEMT has more advantage than the UIT method. For UIEMT sample, fine microstructure with the average grain size of less than 2 mu m was obtained, and the hardening layer was about 2.75 times deeper than the UIT one. The microhardness profile and residual compressive stress distribution showed a good correlation with the microstructural transition. In addition, no martensite transformation can be found by XRD. It was concluded that UIEMT can significantly improve the wear resistance without changing the chemical composition of the material.