Abstract
On the basis of the requirements for protective coatings of molds, the materials of pseudoalloys were determined for applying coatings from two wires. One of the wires is copper, which provides maintaining a sufficient thermal conductivity of the layer, and the second one consists of a material, which provides wear resistance of a coating. As the second wire, the wires NiCr, Mo, Ti and a flux-cored wire were used, consisting of a steel sheath and a filler – FeB powder. Based on the calculation data on the thermal conductivity of coatings, taking into account the coefficients of heat transfer, the estimation of the influence of these coatings on the thermal processes in the mold (temperature of the wall surface, intensity of heat removal from the wall) was performed. Applying electric-arc spraying, the pseudoalloy coatings with a uniform distribution of components were produced, one of which is copper with a hardness of 1,320–1,460 MPa, and the second one is the strengthening component NiCr, with a hardness of 2,440 MPa; Mo, with a hardness of 5,350 MPa; Ti, with a hardness of 7,540 MPa; FeB, with a hardness of 7,050 MPa. As a result of measurements of the coefficient of thermal expansion of coatings, it was found that the coating Cu-NiCr is the closest to the coefficient of thermal expansion of copper. Then it is followed by Cu-FCW (FeB), Cu-Ti and Cu-Mo. The abrasive wear resistance of pseudoalloy coatings at a room temperature exceeds pure copper 1.4–2.3 times. The tests of pseudoalloy coatings for resistance to wear during heating to 350 °C showed that the wear resistance of Cu-NiCr and Cu-FCW (FeB) coatings exceeds the resistance of pure copper 4.5 and 22 times, respectively. The hot hardness of the coating Cu-NiCr in the range of 20–400 °C exceeds the hardness of pure copper 3 times.
Highlights
The efficient and economical way to increase the service life of parts, operating in difficult conditions of high temperatures, aggressive environment and mechanical wear, is the creation of strong and wear-resistant layers on the surfaces.Such parts include elements of metallurgical equipment: molds of continuous casting machines (CCM).In the technological process of continuous casting of steel, mold has one of the most basic functions – formation of an ingot of the required thickness and strength [1]
The spraying of ceramic coatings with high hardness (700–1,600 HV) using the high-velocity oxygen fuel (HVOF) method can significantly increase the service life of molds, the strength of which can reach 1,200 melts [17]
Based on the experiments on electric-arc spraying of pseudoalloy coatings and the obtained results of the investigation of properties, the developed coatings can be recommended for applying on the walls of CCM molds
Summary
The efficient and economical way to increase the service life of parts, operating in difficult conditions of high temperatures, aggressive environment and mechanical wear, is the creation of strong and wear-resistant layers on the surfaces. Such parts include elements of metallurgical equipment: molds of continuous casting machines (CCM). The material of working walls should have high thermal conductivity and wear resistance and should maintain the stability of mechanical properties at elevated temperatures. The methods of applying protective coatings are actively developed using more wear-resistant and heat-resistant materials, which do not have a harmful effect on the quality of steel ingot
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