Fretting Wear Behavior Of HVOF Sprayed Cocrw And WC-10CO-4CR Coatings On The Surface Of Inconel690 Alloy

In the nuclear power system, the fluid transport and energy transfer will cause minute vibrations between the steam generator tube and its support plates, which can lead to the fretting damage. Cracks on the surface of the steam generator tube are initiation and propagation with continued fretting, and it will exacerbate fretting damage. It can also cause burst accident. It will seriously affect the security operation of the system of nuclear power. In supporting the contact portion of heat transfer tube coated with high temperature wear-resistant coating, it can improve the fretting damage resistance of the heat transfer tube, which has important implications for the protection of the safety of nuclear power systems.This paper studies the fretting wear characteristics of WC-10Co-4Cr and CoCrW coatings, which were coating on the surface of Incone1690 alloy tube by High Velocity Oxy-Fuel(HVOF). The fretting wear behavior of the two coatings and Incone1690 tube in contact with crossed corundum cylindrical sample have been investigated on the PLINT fretting wear tester. The experiment conditions:the displacement amplitude of 100～200 μm, the normal load of 100～200 N, the frequency of 2 Hz, the number of cycles of 10000, at room temperature. Based on the existing date, using scanning electron microscope (SEM), optical microscope (OM), electron spectrometer (EDX), X-ray diffraction (XRD), NanoMap500DLS profiler and three-dimensional confocal microscope (OLYMPUS-OLS4100) and some other analysis tools. The fretting wear characteristics and mechanism damages of the two coatings and Incone1690 alloy in the slip region were investigated. The following conclusions:(1) When the normal load is constant, the friction coefficient of the coatings and Incone1690 alloy become large, with the displacement amplitude increasing. Under the same experimental conditions (Fn=200 N, D=150μm, f=2 Hz), steady-state friction coefficients of WC-10Co-4Cr, CoCrW and Incone1690 alloy are 0.56,0.59 and 0.93, respectively.(2) The two coatings wear resistance are significantly better than Inconel690 alloy. And WC-10Co-4Cr coating better than CoCrW.(3) The wear mechanism of the two coatings are mainly abrasive wear and delamination wear; and the Incone1690 alloy is mainly abrasive wear and adhesive wear.(4) The wear scar cross-section of the Incone1690 alloy and the two coatings can clearly show the three-tier structure of the base layer, plastic layer and the debris layer.