Effect of mechanical impact and friction treatment on the microstructure of TIG welding surface

Abstract

Mechanical impact and friction treatment were applied to improve the TIG weld joints surface performance of Q235 steel. The micromorphology and the size of a crystal grain in the treated weld surface were studied by an optical microscopy, microhardness tester, Scanning Election Microscope (SEM) and X-Ray Diffractometer (XRD). It was shown that a thickness of about 400 µm after 20 treatment times could be reached. Meanwhile, the dense refinement layer was formed on the top of plastic deformation layer with the hardness of 370 HV. After 5 treatment times, refinement layer reached a thickness of about 10 µm, and the grain size was about 27.15 nm. With the increase of the treatment times, the thickness of refinement layer increased and the grain size was further refined. As the treatment times reached 20, the thickness of the refinement layer was about 50-60 µm, the micromorphology became the dense fibrous structure, and the grain size was about 10.6 nm.K e y w o r d s : mechanical impact, low-carbon steel, weld, grain refinement