Load Effect On The Translation Of Friction Mechanism Of GCr15, 304 Stainless, SE NiTi And SME NiTi Alloy

By using diamond tips of 2μm and 5μm in curvature radii, the tribological properties of GCr15, 304 stainless, superelastic (SE) and shape memory effect (SME) NiTi alloys were investigated with an atomic force microscopy (AFM) and nano-scratch tester (NST), respectively. The scratch damage of the materials was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and profiler. The study was focused on the effect of lubrication conditions (dry, humid and oil lubrication), material properties (elastic modulus and hardness), and load on the translation of friction mechanism. The main conclusions of the research can be summarized as following:1. The results indicated that the load exhibits a strong effect on the friction mechanism. At low load, the friction mechanism is mainly identified as interfacial friction. While at high load, it is mainly characterized as plough friction. When the load was below 80μN, no obvious damage was observed on four samples and the interfacial friction should be dominated. While the load increased to 100-150μN, the plough friction became dominated. As the load attained 80 mN, more than 90% of the friction force was induced by plough.2. It was also found that the hardness and elastic modulus of materials revealed a significant effect on their friction behaviors. The higher the hardness of material, the more difficult to be ploughed the material, and the larger the translation load between interfacial friction and plough friction. In addition, when the material had higher ratio of elastic modulus to hardness, the plough should be more dominant during the scratch process.3. The pileup of the plastic deformation around scratch was higher and the width of scratch was larger under humid condition. At the load of 80 mN, the wear particle besides scratch was obviously less under oil condition.4. With the increase of the curvature radius of indenter, both the indentation depth and residual indentation depth were gradually decreased, which in turn reduced the friction.