Development of elements of technology for increasing the durability of tractor components from gray cast iron

Abstract

The problems of increasing the durability of tractor parts from ferrite-pearlitic gray iron by using the process of diffusion surface doping with subsequent quenching for martensite are considered. The process of diffusion surface doping of gray iron is realized by heating the alloy in contact with the oxide of alloying elements (chromium, titanium, vanadium, etc.). At the same time, dissociation of the oxide molecule of the alloying element and the diffusion of atoms into the interior of the cast iron occur on the alloy surface. This scheme of the process makes it possible to oxidize the carbon of the cast iron base and simultaneously alloy the surface layer. Studies of the diffusion layer have shown that it has a pearlite structure, which means that it is possible to use the quenching process to obtain a martensitic structure. Important factors that determine the resistance of metals and alloys to wear include their structure, physical and mechanical properties, as well as their mutual arrangement, the quantitative ratio and the nature of the relationship between the individual components of the structure of the material. An important issue in the practical implementation of the technology in is the determination of quenching regimes that provide the required microstructure and properties of the alloy, primarily the heating time for quenching. In this paper, we consider the possibility of applying heat engineering calculations to solve the abovementioned problem. Calculation of the heating parameters for quenching was carried out by solving the heat equation in the criterial form. The heating of a cylindrical part was considered. On the basis of the determination of the Bio and Fourier criteria, heating curves were constructed, which made it possible to determine the desired values of the heat treatment regimes. Experimental verification of the obtained results showed that the microstructure of the alloy is fine-needle martensite, which confirms the applicability of the calculated determination of the quenching regimes.