The influence of heat treatment on structure, mechanical properties and corrosion resistance of steel X10CrNi18-8

Purpose: The aim of the paper is to investigate the influence of the heat treatment on the structure, mechanical properties and corrosion resistance of the steel X10CrNi18-8. Design/methodology/approach: The investigated steel was solution heat treated at temperature 1050°C with water cooling and it was analysed the susceptibility to intergranular corrosion at temperature 700°C. Structures were investigated using light microscopy. The examinations of the mechanical properties were conducted on ZWICK 100N5A. Hardness measurements were made by Vickers method r. The investigations of the precipitation process were done by X-ray diffraction phase analysis. Corrosion resistance of investigated steel was examined using potentiodynamic methods. Findings: The structure of analysed steel in as-cast conditions consist of austenitic microstructure with numerous slip bands in areas with deformation martensite α'. The examined steel after solution heat treatment followed by water-cooling has the structure of austenite with a small amount slip bands. Ageing at 700°C caused precipitation of many chromium carbides on the grain boundaries and inside the grain. The best mechanical properties (UTS=1327 MPa, YS _0.2=1287 MPa, 392 HV) has steel as-cast conditions. It was also found that the investigated steel show poor corrosion resistance in 3.5% NaCl solution. Fractographic analyses of the samples after corrosion tests permitted to define the kind and degree of corrosion damage. Research limitations/implications: To investigate in more detail the corrosion behaviour 18-8 austenitic steels, the investigations should include immersion tests and an analysis of corrosion products. Practical implications: The obtained results can be used for searching the appropriate way of improving the corrosion resistance of a special group of steels. Originality/value: The relationship between the heat treatment, structure, mechanical properties and corrosion resistance of X10CrNi18-8 steel was specified.