Influence heat treatment on the properties and microstructure of castings of complex alloyed irons

Complex-alloyed white cast irons are an extremely important class of structural materials with a combination of unique properties. Mechanical properties such as hardness, strength and wear resistance, as well as the structure of castings from these cast irons are determined by their composition and crystallization conditions, which determine the structural features and mutual arrangement of phases and, to no lesser extent, by the conditions of heat treatment. The metal base of the studied complex-alloyed high-chromium cast irons consists of austenite and its decomposition products (martensite, troostite, pearlite). The amount of austenite decomposition products is determined primarily by the chemical composition and crystallization conditions. Elements that stabilize austenite in the eutectoid temperature range (nickel, manganese, copper, molybdenum) contribute to an increase in the proportion of martensite and troostite in the cast state, and during quenching allow obtaining only a martensitic matrix. This is especially evident in the complex alloying of white cast irons with elements that increase its hardenability and quenchability: Ni, Mo, Cu, Mn, B, Ti. The results of the comparative study clearly illustrate the slight difference in the properties of cast irons with different types of heat treatment. The difference between the minimum and maximum values of hardness and wear resistance does not exceed 15 % on average. Thus, in some cases, it is possible to avoid the expensive operation of heat treatment - normalization, and subject the castings only to tempering at a temperature of 300-400 °C. It is also not recommended to use castings without heat treatment due to high residual stresses, which can contribute to their destruction under operating conditions.