Materials based on cast irons are often used for protection against wear. One of the methods of creating protective surface with cast iron structures is hardfacing. The application of hardfacing with self shielded flux cored wire with high carbon content is one of the economical ways often used to protect machinery parts exposed to both abrasion and erosion. The wear resistance of hardfacings depends on their chemical composition, structure obtained after hardfacing, parameters of depositing process and specific conditions of wear. As the base material in the investigation the steel grade S235JR was used. The wear behavior mechanism of hardfacings made with one type of self shielded flux cored wire and different process parameters were evaluated in this paper. Structures obtained in deposition process were different in hardness, amount of carbides and resistance to wear with two investigated impingement angles. The erosion tests showed that impingement angle 30° gives lower erosion rate than angle 60°.

This work deals with the effect of austempering temperature and time on the microstructure and content of retained austenite of a selected cast steel assigned as a material used for frogs in railway crossovers. Bainitic cast steel was austempered at 400°C, 450°C and 500°C for two selected times (0.5 h, 4.0 h) to study the evolution of the microstructure and retained austenite content. The microstructure was characterized by optical microscopy, X-ray diffraction analyses (XRD), and hardness tests. Phase transformations during and after austempering were determined by dilatometric methods.

The increase in isothermal temperature causes an increase in time to start of bainitic transformation from 0.25 to 1.5 s. However, another increase in temperature to 500°C shifts the incubation time to as much as 11 s. The time after which the transformations have ended at individual temperatures is similar and equal to about 300 s (6 min.). The dilatation effects are directly related to the amount of bainite formation. Based on these we can conclude that the temperature effect in the case of cast steel is inversely proportional to the amount of bainite formed. The largest effect can be distinguished in the case of the sample austempered at 400°C and the smallest at 500°C. Summarizing the dilatometric results, we can conclude that an increase in austempering temperature causes an increase in austenite stability. In other words, the chemical composition lowers (shifts to lower temperatures) the range of bainite transformation. It is possible that at higher austempering temperatures we will receive only stable austenite without any transformation. This is indicated by the hatched area in Figure 4b. This means that the heat treatment of cast steel into bainite is limited on both sides by martensitic transformation and the range of stable austenite. The paper attempts to estimate the content of retained austenite with X-ray diffraction.