304 stainless steel is a common alloy of stainless steel that contains Fe, Cr and Ni elements. It has received extensive attention due to its excellent corrosion resistance mechanical properties and low price 304 stainless steel is widely applied to automotive aerospace, architecture and nuclear industries, etc. However, the friction and wear behavior of stainless steel can significantly affect its performance and service life in different environments and applications. Therefore, studying nano-tribological characteristics and the deformation process of 304 stainless steel is crucial given the fast growth of nanotechnology and advanced materials. Currently, molecular dynamics (MD) simulation has become an effective tool for revealing atomic scale behavior, providing clear insights into potential deformation mechanisms and defect evolution.
The molecular dynamics model consists of a 304 stainless steel and a diamond abrasive, where the 304 stainless steel specimen is divided into a Newtonian layer, a thermostat layer and a fixed layer. The effects of the sliding velocity and pressed depth on wear capacity, friction coefficient, dislocation evolution and shear strain were comprehensively investigated using molecular dynamics simulation in this paper.
The results showed that the average friction force, average normal force and average SCOF under the 15 Å pressed depth was significantly higher than other pressed depths, and the number of wear atoms was significantly the highest. 304 stainless steel had a large amount of atomic displacement and dislocation length at high pressed depth; The smaller range of shear strain under low pressed depth helped to reduce the plastic deformation of 304 stainless steel. At the same pressed depth, the friction force was higher under higher sliding velocity, while the dislocation length decreased. This was due to the lack of sustained driving force for dislocation nucleation inside the alloy at high velocity, thereby reducing the deformation of the alloy. In addition, the friction hear generated promoted the release of internal stress in the sliding friction process, resulting in the formation of discrete structural dislocations, multi node dislocation and dislocation locks (rings), thus preventing further propagation of dislocations and improving the deformation resistance of the alloy. The number of wear atoms calculated in this work was almost linearly proportional to the sliding distance.
In the process of sliding friction, friction heat would produce complex thermal stress changes in 304 stainless steel, which would affect the change of friction coefficient and dislocation nucleation. However, heat promoted stress release, leading to the formation of discrete structural dislocations, multi node dislocations, and dislocation loops (locks), thereby hindering the further propagation of dislocations and improving the deformation resistance of stainless steel. This was completely consistent with the strain hardening theory of 304 stainless steel. In addition, the slip deformation of some Shockley dislocations played a dominant role in the plastic deformation mechanism.
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