Optimization of microstructure and properties in U75V steel rail cladding layers manufactured by laser melting deposition and laser shock peening

Onsite rail repair is essential to ensure service security and reduce operational costs. In this study, laser melting deposition (LMD) was used to repair damaged U75V steel rail. When the substrate of U75V steel rail was pre-heated at 350 degrees C, thermal cycling and heat accumulation characterized using LMD contributed to the formation of a pearlitic microstructure, same as that of the U75V steel rail substrate. Compared with the U75V steel rail substrate, mechanical properties and friction and wear properties of the cladding layers were improved mean-time. To further improve wear resistance, laser shock peening (LSP) was performed on the surface of the cladding layers during post treatment, such that the lamellar Fe3C phase in pearlite was refined into a type of "degen-erated" pearlitic microstructure. The dry friction and wear tests were conducted on the substrate, cladding layers, and cladding layer post LSP. Results indicated that oxidative wear was caused by heat accumulation and the heavy load during the dry friction and wear tests, and ploughing groove and spalling were observed as the main forms of wear. The cladding layers after LSP exhibited minimum wear loss and the best wear resistance.