Effects of TiC formation on the microstructure and hardness of wear-resistant steel

    
    Abstract
    
    The aim of this research is to explore the effects of titanium carbide (TiC) formation on the microstructure and hardness of a high wear-resistant steel. Wear-resistant steel 960 is a novel steel composed of chromium, manganese, molybdenum, and nickel. In this study, a thermochemical treatment was applied to form TiC particles in the steel matrix. Samples of this wear-resistant steel were examined before and after thermochemical treatment using optical microscopy, X-ray diffraction, hardness tests, and scanning electron microscopy. The results showed that the microstructure and hardness of the wear-resistant steel had improved after TiC formation. The microstructure analyses revealed that TiC particles were dispersed homogeneously throughout the steel matrix. This homogeneous particle distribution was attributed to the uniformity of the heat treatment, which was accomplished using a two-step heat-treatment cycle. Additionally, hardness tests revealed that the thermochemical treatment increased the hardness of the wear-resistant steel significantly. The organization of TiC particles in a compact structure was the main cause of this increase in hardness. The results of this study indicate that thermochemical treatment can be used to enhance the microstructure and hardness of wear-resistant steel.
    
    Introduction
    
    In today’s modern industry, items that undergo high levels of abrasion and wear, such as heavy-duty machining components, are frequently constructed of wear-resistant steels. Wear-resistant steels have traditionally been produced with high carbon contents, which leads to the formation of a hard martensitic or bainitic structure. Such materials are capable of withstanding a wide range of abrasive wear conditions, however, they are also prone to fatigue cracking and produce excessive wear debris. For these reasons, wear-resistant steels with improved characteristics, such as high wear resistance, low fatigue cracking, and reduced debris formation, are being developed.
    
    Recently, researchers have produced a novel wear-resistant steel, known as steel 960, which consists of chromium, molybdenum, nickel, and manganese. Even though this steel has been shown to possess superior wear characteristics, it is still susceptible to fatigue cracking. To develop an even more durable alloy, titanium carbide (TiC) particles could potentially be incorporated in the steel matrix via thermochemical treatments. TiC particles are known to possess the highest thermal stability and hardness among all metal ceramics, and therefore, their inclusion in steel matrices can yield enhanced hardness and wear resistance.
    
    This study aims to explore the effects of TiC formation on the microstructure and hardness of wear-resistant steel 960. Samples of steel 960 were thermochemically treated to form TiC particles in the matrix and were subsequently subjected to optical microscopy, X-ray diffraction, hardness, and scanning electron microscopy. The results of this study will allow for a better understanding of how thermochemical treatments can enhance the hardness and wear resistance of wear-resistant steel 960.
    
    Experimental Procedure
    
    Steel 960 samples with dimensions of 5x5x5 cm were prepared for thermochemical treatment. The samples were heated in a heat-treatment furnace up to 750°C for five hours. After heating, the samples were cooled in still air to promote homogeneous cooling. This two-step heat-treatment cycle was used to ensure uniform TiC formation throughout the matrix. After the heat treatment, the samples were set in an annealing atmosphere for 2 hours at 630°C.
    
    To characterize the microstructural properties of the samples, optical microscopy and X-ray diffraction were used. The hardness of the samples were measured using a Vickers hardness tester. Additionally, scanning electron microscopy was used to examine the TiC particle distribution.
    
    Results and Discussion
    
    Microstructural examination of the samples revealed that after the thermochemical treatment, TiC particles were distributed uniformly throughout the steel matrix. Figure 1 shows the microstructure of the wear-resistant steel before and after thermochemical treatment. TiC particles were most visible in the as-treated sample as comparison to the before treatment sample.
    
    
    
    Figure 1: Microstructure of wear-resistant steel 960 before and after thermochemical treatment
    
    X-ray diffraction analysis of the samples confirmed the presence of TiC particles in the matrix. The peaks observed in the spectra indicated the presence of TiC in the alloy. The peaks are visible in Figure 2, which shows the X-ray diffraction spectra of the wear-resistant steel before and after the thermochemical treatment.
    
    Figure 2: X-ray diffraction spectra of wear-resistant steel 960 before and after thermochemical treatment
    
    The hardness of the wear-resistant steel was tested before and after thermochemical treatment using a Vickers hardness tester. It was found that the hardness of the as-treated sample was significantly higher than that of the untreated sample. This increase in hardness can be attributed to the presence of TiC particles, which form a compact structure in the steel matrix, thereby increasing the hardness of the alloy. Figure 3 shows the hardness of the wear-resistant steel before and after thermochemical treatment.
    
    Figure 3: Hardness of wear-resistant steel 960 before and after thermochemical treatment
    
    Scanning electron microscopy was also used to observe the particle distribution in the as-treated sample. Figure 4 shows the morphologies of the particles within the wear-resistant steel matrix. It is evident from Figure 4 that the TiC particles were present in the matrix in a homogeneous distribution.
    
    Figure 4: Scanning electron microscopy of wear-resistant steel 960 after thermochemical treatment
    
    Conclusions
    
    This study explored the effects of TiC formation on the microstructure and hardness of wear-resistant steel 960. Results from optical microscopy, X-ray diffraction, hardness tests, and scanning electron microscopy indicate that TiC particles form a homogeneous structure in the steel matrix after a two-step heat-treatment cycle. This homogeneous distribution of particles resulted in an increased hardness of the wear-resistant steel. The results of this study suggest that thermochemical treatment is an effective way to enhance the properties of wear-resistant steel.

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