Study On Composite Fretting Wear Behavior Of Two Steels

In industry , the fretting phenomenon is complex. Not only the contact modes are various and the character of the load is daedal, but also the relative displacement may be the composite movement compounded of two or more basic modes including tangential, radial, rational and torsional fretting. The absolute majority of researches have been focused on the fretting of single mode before, the research concerning composite fretting recieved much attention recently.The composite fretting tests with GCr15/60Si2Mn steel or GCrl5 /20 steel ball-on-flat contact have been carried out under the oblique angles of 45?and 60? The maximum imposed loads are varied from 200N to 800N at a constant loading speed of 6 mm/min. The kinetic behaviours of composite fretting tests were analyzed in detail in combination with microscopic examinations through optical microscopy, scanning electrical microscope (SEM), energy dispersive spectroscope (EDX) and confocal laser scanning microscope(LCSM).The main research works and obtained conclusions are as follows:1. There were three basic types of load-displacement (F~D) curves including qusi-trapeziform cycle, elliptic cycle and linear cycle. The feathers of combination of tangential and radical fretting modes were strongly presented in these curves. Corresponding to the three types of F~D curve, the kinetic process of composite fretting might be outlined as three stages.2. The variations of the load-displacement curves as function of number of cycles were strongly depended upon the load levels, oblique angles and the characteristics of materials.3.During the running-in period of composite fretting, the energy of dissipation was increasing with the increasement of the cycle number. After that, the energy of dissipation was lowing with the increasement of the cycle numberbecause of the work-harding of materials.4. Different damage stages corresponding with three load-displace ment curves were analysed in detail in this thesis, The main feature of wear in stage I was slip, and the main wear mechanism was particles detachment by delamination in stage II and HI with different extent.5.In the procedures of wear, oxidizing action is obvious in stage II and III. The extent of oxidation is more intensive in stage II than in stage III.