Study on the friction and wear behavior of laser surface strengthened railway steel

Abstract

It is known that the rail-wheel mechanical system serving in rolling contact conditions may easily get damaged such as friction wear, contact fatigue and so on. In this report, laser surface strengthening of a wheel-shaped high carbon manganese rail steel (U71Mn) was studied under laboratory experiments on a friction and wear tester. The tester has simulated rolling speed, the experiment cycles, the axial loads of the friction discs, and the contact spot size was calculated based on the theory of Hertz elastic contact. Hardened depth and abrasion loss including weight and diameter in multi-parameters were detected. Microstructure, wear resistance and cracking characters were analysed. The experimental results indicated that Rockwell hardness was raised from 20HRC to approximately 50-62 HRC due to the martensitic zone on the surface produced by laser surface strengthening. The wear resistance was enhanced and the grinding depth decreased with the increasing of the hardening depth. Untreated specimen got the maximum abrasion. Under the same experiment cycles, less abrasion occurred in larger Rockwell hardness values and it is also found that there is a competition relationship between the wear resistance and the fatigue-cracking resistance for rail steels, and the wear resistance and the fatigue-cracking resistance should be optimally matched.It is known that the rail-wheel mechanical system serving in rolling contact conditions may easily get damaged such as friction wear, contact fatigue and so on. In this report, laser surface strengthening of a wheel-shaped high carbon manganese rail steel (U71Mn) was studied under laboratory experiments on a friction and wear tester. The tester has simulated rolling speed, the experiment cycles, the axial loads of the friction discs, and the contact spot size was calculated based on the theory of Hertz elastic contact. Hardened depth and abrasion loss including weight and diameter in multi-parameters were detected. Microstructure, wear resistance and cracking characters were analysed. The experimental results indicated that Rockwell hardness was raised from 20HRC to approximately 50-62 HRC due to the martensitic zone on the surface produced by laser surface strengthening. The wear resistance was enhanced and the grinding depth decreased with the increasing of the hardening depth. Untreated specimen got th...