The Research On Wear Behavior Of High Chromium White Cast Iron And 7CrMnMoS Steel

Because of the high wear resistance to abrasives high chromium white cast iron is widely used in foundry equipments. In this paper, imported high chromium white cast iron pipe with perfect wear resistance was used as objective material. In order to interpret the reason to its high wear resistance, microstructure of the white cast iron was systematically studied. Metallurgical structure research and XRD research both demonstrate the high Cr white cast iron with high hardness martensite and alloy carbide rods. Pin-on-disk testing shows its relative wear resistance is 2.5 times higher than normalized 45# steel. Moreover, according to the research on wear surface morphology and wear particle morphology, the wear failure of high chromium is main caused by substrate micro-cutting and micro-ploughing and the fracture of alloy carbide rods.Free-cutting steel 7CrMnMoS independently researched and developed by laboratory was used as experimental material. As good machining performance and good mechanical properties is needed, 7CrMnMoS was quenched and tempered as tempered sorbite as the final microstructure. In this paper, repeated quenching and tempering processing was used to not only refine the grain size and but also keep the microstructure as tempered sorbite. Good wear resistance is also desired to be obtained by the processing. And then, pin-on disc and pin-on-ring machine were both used to test wear loss. And the results show that no matter dry or wet conditions the wear resistance of 7CrMnMoS increases with the quenching and tempering numbers. Single scratch experiment model was used to give a good explanation. In addition, abrasive wear mechanism was also studied, and micro-cutting, micro-ploughing and micro-fatigue were all discovered during wear process.Pin-on-ring dry sliding wear test results indicate that the wear mechanism is plastic deformation dominated and oxidation- supplemented combined wear mechanism. This mechanism was later proved by wear surface morphology, wear particle morphology, subsurface microstructure, subsurface hardness distribution. The results also show the dry sliding wear resistance has close relationship with wear condition. Under the condition of low load and speed, wear loss increases with the quenching and tempering numbers and then slightly decreases. When the load and speed reach a high level, wear loss obviously shows decreasing trend with the increase of quenching and tempering numbers. The reason to the results we observed is that the size effect strengthening mechanisms works during the wear process. With the increase of load and speed, the thickness of the worn surface caused by wear process will increase and the grain refinement strengthening mechanism will work effectively.