Study on Microstructure Evolution and Wear Resistance Properties of Laser Cladding Applied on R900A Rail Steel

The current research aimed to study microstructure evolution and wear resistance properties of coating layers on R900A rail steel. Powdery type laser cladding was carried out employing a three-jet coaxial laser nozzle by using the 3650 (Chromium-Nickel steel) powder. The key laser cladding parameters included a laser power of 1 - 1.5 kW, a scanning speed of 5 - 15 mm/s, and a powder feed rate of 10 – 20 g/min. After laser cladding completion, the coated specimens were carried out into the pin-on-disc tribometer for abrasive wear resistance evaluation compared to the reference rail material. The specimens were weighed before and after the wear test by an electronic balance with 0.0001g resolution. The hardness test and microstructure evolution were performed on the cross-sectional area of the specimen. After the wear test, the worn surface profile and wear morphology of the tested specimen were evaluated to determine the wear mechanism and severity. The hardness test shows that the 3650 had a higher hardness than the conventional rail steel. The microstructure of coating surfaces was composed of various carbide compounds such as Cr 23 C 6 and Cr 7 C 3 , which are distributed in the austenite matrix. Moreover, the 3650 cladding surface provided greater wear resistance than rail steel and not much difference in hardness, which is suitable for rail maintenance in a realistic situation.