Effect of Tempering Temperature on Precipitation Behavior of TiC Particles in TiC Reinforced Wear-resistant Steel

The presence of TiC particles in the wear-resistant steel can provide high wear resistance and excellent comprehensive performance. The size, distribution and structure of TiC particles after tempering are decisive factors affecting the wear performance, so the precipitating behavior of TiC particles in wear-resistant steel is one of the important characteristics to be evaluated. The tempering temperature affects the precipitation of TiC particles, and the effects are as follows.
    
At low tempering temperatures (below 500°C), the traditional grain coarsening, tempering softening, precipitation of oxygen and nitrogen, and some decomposition of carbides occur. Although TiC particles increase in size, the growth is limited and the number of particles remains roughly unchanged. At this time, most eutectic carbides are of primary TiC particles, and a small amount of compounds are formed, mainly Al2Ti and Ti(C,N).
    
At higher tempering temperatures (between 500°C and 600°C), the size of TiC particles begins to increase, and the number of secondary TiC particles generated by the solid solution of elements begins to increase, resulting in a decrease in the total number of primary TiC particles. At the same time, Al2Ti, Ti(C,N) and other TiC compounds are produced, and some primary TiC particles are decomposed into Al2Ti and Ti(C,N). The maximum total volume fraction of TiC particles can reach about 80%. When the tempering temperature exceeds 600°C, the number of primary TiC particles begins to decrease, and the ratio of substances to particulate TiC increases. The average size of primary TiC particles increases and changes in a discontinuous form.
    
In general, the increase of tempering temperature can increase the mean particle size of TiC, broaden the particle size distribution range and increase the total volume fraction of TiC particles. But excessively high tempering temperature can cause precipitation of TiC particles, reducing total volume fraction of particles and forming fewer numbers of particles. Therefore, it is necessary to determine the optimum tempering temperature for TiC reinforced wear-resistant steel according to the practical application.

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