Tangential Fretting Wear Characteristics of Inconel 718 Laser Melting Alloy Layer

As a new method of components damage repair, laser cladding deposition technology has been widely used in the repair of aeroengine turbine blades. Turbine blade is the key component of aero-engine power energy device, fretting wear is one of the main reasons for its fracture failure. Therefore, exploring the fretting damage characteristics of laser cladding deposited nickel base alloy is great significance to the safe service of repaired aeroengine. In this study, the tangential fretting wear tests were carried out by using the self-developed multi-functional composite fretting wear tester under the point contact mode of ball-on-flat. The fretting wear characteristics of the Inconel718 alloy samples prepared by laser cladding deposition under different normal loads (F_n =10, 25, 50 N) and different displacement amplitudes (D=100, 200 μm) were investigated. After the tests, the dynamic characteristics of the obtained friction displacement curve, friction coefficient curve and dissipated energy were analyzed in detail, and the main fretting mechanism of the sample in the process of fretting wear was obtained. The wear morphology of the surface and section of the sample were analyzed by scanning electron microscope, and the main damage and wear mechanism of the sample in the process of fretting wear were obtained. The micro element composition of the damaged area was analyzed by electronic energy spectrometer, and the fretting wear damage mechanism was further explored. The three-dimensional wear morphology of the sample was analyzed by three-dimensional profiler, and the wear volume of the wear mark was measured. The results show that when the displacement amplitude was 100 μm and the normal load was 10N, the friction force displacement curve was an obvious parallelogram shape, and the fretting wear running in the gross slip regime. When the displacement amplitude was 100 μm and the normal load increases to 25 N, the friction displacement curve showed the mutual transformation between ellipse and parallelogram, and the fretting wear was running in the mixed slip regime. As the same, when the displacement amplitude increased to 200 μm and the normal load reached 50 N, the friction displacement curve showed the conversion between ellipse and parallelogram, and the fretting wear was running in the mixed slip regime too. Under the same displacement amplitude, with the continuous increase of normal load, the fretting wear was running changed from gross slip regime to mixed slip, and the damage of materials were gradually aggravated. The integral area of the figure surrounded by the friction force displacement curve increased gradually, and the energy dissipation caused by fretting wear increased. The volume, width and depth of the wear scar increased gradually. The friction coefficient curve obtained in the fretting tests showed three stages: rising stage, falling stage and stabilizing stage. Moreover, when the normal load was constant, with the increase of displacement amplitude, the two contact bodies were more prone to relative slip and the wear damage of materials was intensified. The fretting damage evolution law of materials were changed with the continuous progress of fretting test. Firstly, the fretting damage zone appeared large peeling and massive wear debris, and with the initiation and propagation of cracks. As the test continue, the massive wear debris was peeled and broken, finally a large amounts of fine wear debris were formed. The main mechanisms of fretting wear of Inconel 718 alloy samples prepared by laser cladding deposition were fatigue wear, oxidation wear and abrasive wear.