Study On The Fretting Corrosion Behavior Of Steels

With the development of ocean engineering, chemical industry and aerospace industry, as well as the wide application of medical implanting material in body, the harmfulness of fretting corrosion becomes more and more important. While up to now, main of the research on fretting has been focused on the fretting wear and fretting fatigue in air, few publications on the fretting corrosion in water are found in the literatures and the systematic studies on the mechanism of fretting corrosion are even more limited. Therefore, referred to the real conditions in the industry, the fretting corrosion behavior of typical steels in kinds of fluidic mediums has been investigated in this thesis. The interaction between the wear and corrosion was discussed. The studies will not only show its significant importance in industry, but also exhibit an important academic value.The fretting corrosion experiments were performed by a hydraulic fretting test rig equipped with liquid container and cathode polarization device. The systematic studies have been conducted on the fretting corrosion behavior of three typical steels (45# steel, GCr15 steel and 0Cr18Ni9 stainless steel) in eight different fluidic mediums (air, pure water, acidrain, seawater, two lubricating oils, water film, and oil/water emulsified film). Combined with the analysis on the frictional dynamic behavior, the fretting corrosion scars have been carefully characterized through optical microscope, scanning electrical microscope (SEM), laser confocal scanning microscope (LCSM) and energy dispersive spectroscope (EDS).The main research works and obtained conclusions are listed as following:1. Pure water and acidrain could transform the partial slip regime of steels (45# steel, GCr15 steel and 0Cr18Ni9 stainless steel) to small displacement amplitude, resulting in a wide mixed regime and gross slip regime. Seawater could transform the partial slip regime of 0Crl8Ni9 stainless steel to small displacement amplitude, but almost had not effect on the other two steels.2. All the fluidic mediums, such as pure water, acidrain, seawater and lubricating oils, exhibited lubricating effect and decreased the friction coefficient of contact pairs especially in gross regime. It was found that the value of steady friction coefficient was depended on the fluidic medium property and experimental conditions. Compared to water mediums, the oil/water emulsified film showed better lubricating effect.3. The wear lost of three steels in water mediums, such as pure water, acidrain and seawater, was relatively lower, showing a "negative" interaction of wear and corrosion. The wear lost of 45# steel in acidrain was similar as that in seawater, and both were lower than that in pure water. The wear lost of GCrl5 steel in pure water and seawater was lower than that in acidrain. The wear lost of 0Crl8Ni9 stainless steel in pure water was higher than that in seawater but lower than that in acidrain. In air, pure water and lubricating oil, the wear damage degree and wear lost of 45* steel and GCrl5 steel decreased in turn. Similarly, in air, water film and oil/water emulsified film, the wear rate of GCrl5 steel and 0Crl8Ni9 stainless steel decreased successively.4. In water mediums, the main fretting corrosion damage mechanism of three steels was the joint of abrasion, delamination and corrosion. In acidrain and seawater, the corrosion products were generated for three steels. The corrosion of 45* steel and GCrl5 steel was more serious than that of 0Crl8Ni9 steel. Except that few corrosion product and wear debris stayed in wear area and became the third body, main of them were moved out during fretting process. The third body composed of corrosion product and wear debris joined in the fretting and affected the fretting corrosion behavior of steels.5. In acidrain and seawater, the effect of cathode polarization on the fretting corrosion behavior has been investigated. The results indicated that the cathode polarization increased the friction coefficient and decreased the fretting corrosion wear rate. Fretting wear could also decrease the voltage of the contact surface of the metal material and increase the surface active. The generation, development and stability of the fretting corrosion product film were relative to...