Improving the Wear Resistance of Tillage Machines Details
The study was carried out to study the physicomechanical properties and microstructure of grey cast iron when applied on a steel base of operative parts of tillage machines (ploughshares) as a wear-resistant material. Grey iron was first subjected to heat treatment consisting in hardening in the temperature range of 750-1050 C followed by cooling in water and annealing at a temperature of 900 C for 1 h. The research program included a comparative analysis of a reference sample and samples subjected to preliminary heat treatment. The tensile strength of grey cast iron after heat treatment reached 200-250 MPa. After tempering at 300 С its hardness increased to HRC 50-55 without the subsequent formation of hardening cracks. The best method of heat treatment of grey cast iron was hardening at a temperature of 900 С followed by cooling in water. The material was applied on the tillage tool by an electric arc and electrospark deposit welding. The microstructure of the deposited layer became perlite ledeburite without precipitation of graphite. Electrospark application allowed for the formation of a wear-resistant layer in several cuts, while the structure of cast iron and the base did not change. We did not observe an increase in granularity in the deposited layer that favourably affected its properties. The hardness of the deposited layer was higher (4800-5000 MPa) than that of the base metal (2300-2400 MPa); softening of the base was not observed. According to the results of field tests, heat-treated grey cast iron can be recommended for use as a material for hardening, since the coating thickness did not lead to changes in the initial geometric dimensions of the tillage tool.