Microstructure evolution and wear resistance of in-situ nanoparticles reinforcing Fe-based amorphous composite coatings

The crack-free Fe-based amorphous composite coatings were successfully prepared on stainless steel substrates by optical laser processing technology. XRD characterization exhibited the composite coating mainly consisted of Fe (Cr, Mo) solid solution and a little of Fe5C2 and Fe23B6 reinforcing particles. The main crystalline diffraction peaks gradually broadened with the increase of scanning rates, and the maximum volume fraction of amorphous could reach 50%. The microstructures of the composite coating transformed from coarse columnar and cellular to uniform dendrites, and eventually into disorder amorphous matrix along with a few nano-sized precipitates with the increase of scanning rates. The micro-hardness dramatically improved due to the increased content of amorphous phases and in-situ nanocrystalline reinforcing, which would be beneficial to improve the wear resistance of the composite coatings. Severe plough groove cutting and delamination obscission caused by massive debris and oxidation aggravated the wear failure of the substrates. In contrast, slight adhesive wear was the dominant wear mechanism of the coating, while severe adhesive wear caused by substantial element transfer occurred for the counter Si3N4 balls during the worn process.