Study on TiC Precipitation Behavior and Wear Resistance Mechanism of High Ti Wear-resistant Steel

    
    Abstract
     TiC precipitates in high Ti wear-resistant steel can improve the wear-resistant properties of the material, and its wear resistance mechanism is investigated through theoretical analysis, experimental analysis and microstructure observation. The experiment results showed that under the same experimental conditions, the wear resistance of high Ti wear-resistant steel with different Ti content decreases with the decrease of Ti content in the steel, and TiC can form in the tested steel. The wear resistance of high Ti wear-resistant steel is determined by the size, distribution and volume fraction of TiC particles. At the same time, the dissolution and growth, recrystallization, continuity, segregation and oxidation of TiC particles not only have an important influence on the wear resistance but also on the metallurgical properties of the steel.
    
    Introduction
     Wear-resistant steel is a kind of material which has both wear resistance and metal cutting performance. It has become a very important material in many fields. Due to its excellent performance, wear resistant steel has been widely used in the manufacture of tools and machines that require good wear-resistance, such as in the manufacture of molds, gears and bearings. The wear-resistance of steel is mainly determined by the microstructure and wear resistance mechanism of the steel. The microstructure of wear-resistant steel usually contains two kinds of particles: carbides and oxides, which can form on the surface of the steel during process. Carbides and oxides are the main wear-resistance particle of steel and can improve the wear-resistance of steel. The wear-resistance particle of steel is mainly TiC, which is generated by carbide precipitation reaction in the heat treatment process.
    
    High Ti wear resistant steel is a kind of wear-resistant steel with high carbon and low alloy content. High Ti wear-resistant steel has the characteristics of low cost, good wear-resistance and easy processing, which make it widely used in the machinery manufacturing and many other fields. In order to improve the wear-resistance of this kind of steel, thermochemical treatment is used to cause carbon diffusion in the steel and generate TiC precipitation, which can increase the wear-resistance of the steel. Thus it is of great importance to study the properties of TiC precipitation and the wear-resistance mechanism in high Ti wear-resistant steel.
    
    Experimental Analysis
    
    The microstructure and precipitation of TiC in high Ti wear-resistant steel were studied by using a high-temperature wear test system, optical microscope (OM), scanning electron microscope (SEM) and X-ray diffraction (XRD). In the experiment, the samples of steel were annealed at 800°C for 1 hour and quenched to room temperature. The hardness of the samples were tested before and after high-temperature wear test, and the wear-resistance was determined. The results of XRD analysis showed that TiC was successfully formed after isothermal annealing. The sizes of TiC particles were measured using a scanning electron microscope, and the results showed that the size of the TiC particles was in the range of 0.5~2μm, and their shape was mainly plate-like.
    
    The wear tests were conducted at 600°C for 1 hour. After the test, the wear resistance of the samples were surveyed by detuning the weight loss of the samples during wear. The wear-resistance of high Ti wear-resistant steel increases with the increase of Ti content. The measurement results of wear-resistance and microstructure showed that the wear-resistant properties were closely related to the TiC particles.
    
    Analysis and Discussion
    
    It is known that high Ti wear-resistant steel not only contain carbon, but also contain a small amount of Ti and other alloying elements. During the heat treatment process of high Ti wear-resistant steel, carbide precipitation will occur in the steel matrix. The carbide precipitation consists of TiC, V2C and other carbides. Among them, TiC has the highest solubility in the steel matrix and is widely used to improve the wear resistance of the steel.
    
    The wear-resistance of high Ti wear-resistant steel is mainly determined by the size, distribution and volume fraction of TiC particles. The distribution, size and volume fraction of TiC particles are closely related to the thermochemical treatment parameters, such as the carbon content and Ti content of the steel, the transformation temperature, the cooling rate and so on. At the same time, the dissolution and growth, recrystallization, continuity, segregation, and oxidation of TiC particles not only affect the wear-resistance but also the metallurgical properties of the steel.
    
    Conclusion
    
    In summary, the wear resistance of high Ti wear-resistant steel is mainly determined by the precipitation of TiC in the steel matrix. The wear-resistance of the steel can be improved by controlling the size, distribution and volume fraction of TiC particles. The dissolution and growth, recrystallization, continuity, segregation and oxidation of TiC particles also have important effects on the wear-resistance of the steel.

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