STUDY ON THE FRICTION AND WEAR BEHAVIOR OF LASER SURFACE STRENGTHENED RAILWAY STEEL

摘要

It is known that the rail-wheel mechanical systemserving in rolling contact conditions may easily getdamaged such as friction wear, contact fatigue andso on. In this report, laser surface strengthening ofa wheel-shaped high carbon manganese rail steel(U71Mn) was studied under laboratoryexperiments on a friction and wear tester. Thetester has simulated rolling speed, the experimentcycles, the axial loads of the friction discs, and thecontact spot size was calculated based on thetheory of Hertz elastic contact. Hardened depthand abrasion loss including weight and diameter inmulti-parameters were detected. Microstructure,wear resistance and cracking characters wereanalysed. The experimental results indicated thatRockwell hardness was raised from 20HRC toapproximately 50-62 HRC due to the martensiticzone on the surface produced by laser surfacestrengthening. The wear resistance was enhancedand the grinding depth decreased with theincreasing of the hardening depth. Untreatedspecimen got the maximum abrasion. Under thesame experiment cycles, less abrasion occurred inlarger Rockwell hardness values and it is alsofound that there is a competition relationshipbetween the wear resistance and the fatiguecrackingresistance for rail steels, and the wearresistance and the fatigue-cracking resistanceshould be optimally matched.