Improvement in Fretting Wear Properties of AISI 4135 Steel by Laser-Cladded Martensitic Stainless Steel Coatings

To inhibit the fretting wear of the locking mechanism of the variable-gauge high-speed trains, the substrate (AISI 4135 steel) was treated by laser cladding with 420 martensitic stainless steel powders. The microstructure and fretting behavior of substrate and cladding layers under different laser powers and scanning speeds were analyzed. The results showed that the microstructure of the cladding layer mainly was lath martensite and carbides, with the formation of alpha-Fe, (Fe, Cr) solid solutions, Fe3Si, carbides (Fe, Cr) 23C6, and Fe3C cementite phases. Compared with the substrate, the surface hardness of the cladding layer increased from 290 HV0.2 to 478-587 HV0.2, and the wear rate decreased by 51-81%. Besides, adhesive wear, fatigue wear, and oxidation wear were the main wear mechanisms of the substrate. However, only abrasive wear and oxidation wear were found on the cladding layer. The strengthening mechanism of the cladding layer was mainly attributed to the strengthening effect of grain refinement, solid solution, and precipitation phase.