Tribological Characteristics Of 304L Stainless Steel And As-deposited Nickel-based Surfacing

The tribological characteristics of 304L stainless steel and as-deposited PTA surfacing of Ni50 were investigated to explore the wear mechanism of stainless steel used in nuclear pump. The phase transformation of meta-stable austenite to martensite was detected by optical microscope and X-ray diffractometer after the wear test. The friction coefficient changed with the wearing time under different loads was recorded by MMS-2A wear tester. The variation of wear loss and wear rate were measured after the wear test under different load and time. The worn surface morphologies of the material were observed by a JSM-5600LV SEM, in order to analyze the wear mechanism of the material.The results showed that the martensite phase transformation had occured during wearing test of 304L. The weight loss of the material increased with the increasing of wear time. For the reasons of the plastic deformation, martensite phase transformation strengthening, as well as the formation of lubrication layer by oxidized debris, the wear rate of the material decreased with the increasing of wear time. Because of the fatigue delamination, at the applied load of 120 N, the weight loss and wear rate was much higher than that of the applied load of 70 N which doesn't show significant difference from that of 30 N. The wear mechanism was adhesive and abrasive wear under different loads at initial stage during the wear test. And then the main wear mechanism changed with the time and loads. Under the wear test of 30 N, the wear mechanism was adhesive, abrasive and oxidation wear. Under wear test of 70 N for 30 and 90 min, the wear main mechanism was adhesive and oxidation wear; for 180 min, pitting corrosion had occurred. Under wear test of 120 N for 30 min, the wear mechanism was adhesive wear; for 90 min, the main wear mechanism were adhesive and abrasive wear; for 180 min, fatigue wear was detected at worn surface.The research on the microstructure, tribological characteristics of Ni50 surfacing coating showed that Ni50 surfacing deposit composed of heat-affected, bonding zone, center and top fusion zone, the microstructure consists ofγ(Fe, Ni) and CrB, Cr23C6. There were no transformations of austenite to martensite after wear test. Compared to 304L stainless steel substrate, the wear resistance of surfacing deposit has been greatly improved. The main wear mechanism changed with the wearing time and the applied load. At shorter experimental time, the wear mechanism was abrasive wear under lower load, while it was adhesive wear under higher load. At longer wearing time, the wear mechanism was adhesive and oxidation wear under lower load, while it was fatigue and oxidation wear under higher load.