The effects of different heat treatment  regimes on the wear properties

Abstract

In this study, different heat treatment regimes, such as sintering, sintering with low-pressure cementation, and only low-pressure cementation were applied to pure Fe and 0.2 and 0.4% graphite reinforced with Fe-based composite materials produced by powder metallurgy (PM) technique. Detailed studies were carried out on the effects of applied heat treatment modes on the cementation depth, hardness profiles, and wear behavior of PM samples. Field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to analyze the microstructure and worn surface. In addition, the volume loss, specific wear rate, and coefficient of friction were studied to determine the wear behavior of the PM parts. Cementation heat treatment was shown to significantly increase the hardness while increasing the carbon concentration in the surface areas of PM parts. Low-pressure cementation alone offers a greater depth of carbon diffusion than a combination of sintering and low-pressure cementation. The highest hardness increase was observed only in the surface areas of the samples with the low-pressure cementation applied. The hardness values of the samples drop from the surface toward the center. With the increase in carbon concentration, the hardness also becomes greater. The highest wear resistance rate was obtained in the sample with a graphite content of 0.4%, and only the low-pressure cementation method was applied. The worst wear resistance was found in the sample of non-reinforced and only sintered particles. The lowest volume loss and specific wear rate were obtained with Fe + 0.4% graphite reinforcer with only low-pressure cementation heat treatment applied. Thus, no additional sintering is required during the cementing process for Fe-based PM parts. It was concluded that the tribological properties of Fe-based materials could be improved with reduced costs through the cementation process alone, reducing the number of thermal treatments.