Study of the dynamic’s indentation effect with controlled energy on the tribologically transformed surfaces: analysis of microhardness of copper using response surface methodology

Abstract

Under some conditions of impact, it was possible to cause irreversible changes on the surface of solids. Therefore, we performed impact tests with controlled energy (0.15 mJ) to study the general phenomena of surface degradation in complex conditions. On the other hand, we could establish a capacity to produce tribologically transformed surface (TTS). For the first time, our study is based on an analysis of curves and micrographs to know the evolution of the impact’s effect, and the values of microhardness Vickers and chemical analysis. The micrographic observations illustrate the infiltration of aluminum or tin in copper as veins form, lunures or waves in a lenticular zone (hardened) of copper. In addition, EDX analyzes performed in the aluminum absorption in copper didn’t reveal any alloy formation. The mechanisms responsible for its transformations are unknown, it appears that modelization based on dynamic recrystallization and mechanical alloying or adiabatic shear can provide some answers. Concerning modeling, we have elaborate microhardness model in the case of dynamic indentation by exploiting the response surface methodology (RSM), using a quadratic regression model. Combined effects of four impact parameters on the performance outputs microhardness is explored by a statistical analysis of variance (ANOVA). Results show that the microhardness is influenced principally by nature of samples, nature of ball, and height of projection ball. Also, it is indicated that the penetration depth is the dominant factor affecting the microhardness.