Abstract
This work compares the tribological behavior of surface layers obtained by three different hardening processes. The layers were formed on the surface of AISI 4140 steel by applying three different thermochemical treatments. Wear resistance was evaluated using a standardized tribological machine for abrasive wear, according to the limits established by the ASTM G65 “Standard Test Method for Measuring Abrasion Using Dry Sand/Rubber Wheel Apparatus”. According to the results, the boride layers exhibited the highest wear resistance, as compared to nitrided and carburized layers. In contrast, the carburized layers presented the highest loss of volume. Scanning electron microscopy (SEM) was used to analyze the worn surfaces to examine the wear mechanisms. Abrasive wear was identified in all the samples, as the main abrasive wear mechanism. The mean values of the coefficient of friction (CoF) of the hardened surfaces were 0.39, 0.55, and 0.65 for carburizing, nitriding, and boriding samples, respectively, indicating that the wear process may not always be related to a low CoF. The results suggest that the highest hardness is normally associated with high wear resistance, but the coefficient of friction could be not directly related to the hardness of the materials. Finally, a statistical study demonstrates the random nature of the layers obtained by three different hardening processes.
Highlights
IntroductionThe study and understanding of this phenomenon are essential due to the fact that friction between mechanical elements can lead to economic losses of approximately 0.5% of the gross domestic product (GDP) in developed countries [2]
Modeling the boride layer growth is helpful as it could optimize the industrial manufacturing processes where different devices and pieces, such as those described in Table 1, are used together as well as the quantity of raw material and energy to create the layer according to the size of the piece
During the surface-hardening processes applied to the samples, layers with different thicknesses and harnesses were obtained
Summary
The study and understanding of this phenomenon are essential due to the fact that friction between mechanical elements can lead to economic losses of approximately 0.5% of the gross domestic product (GDP) in developed countries [2]. The problem of wear is present in all kinds of industries, even in orthopedic surgery, where one of the main problems encountered with hip and knee prostheses is aseptic loosening. This problem has been associated with the tissue reaction to wear particles of the implant material produced by friction between the contacting surfaces [3]. The use of lubricants between two sliding solids can reduce friction and, the wear on the materials
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