Abstract
High chromium white cast iron (HCWCI) is considered as one of the most useful wear resistance materials and their usage are widely spread in mining and engineering industry. The wear resistance and mechanical properties of HCWCI mainly depend on the type, size, morphology of carbides and the matrix structure, i.e. austenite or martensite. Cast components of HCWCI are relatively cheap to produce which makes them highly demanded in the mineral processing, power plant, cement industries, etc. However, residual stresses in HCWCI alloys can compromise their application and service-life. Currently there is not enough literature to properly model and predict the residual stresses produced when casting HCWCI components. To meet the need of practical production for the HCWCI manufacturing processes, simulation work on different manufacturing process is a feasible method for HCWCI castings. A hypoeutectic composition of HCWCI material was designed and manufactured to simulate the real manufacturing processes as closely as possible. Hole-drilling method (HDM) and MAGMASOFT simulation program were used in this present study to measure residual stresses of the castings at different positions and/or depth. The stress measurements were determined on the produced alloy or casting in the as-cast conditions, full annealing and machined conditions From the preliminary investigation, i.e. HDM, it was observed that the surface of a casting had excessively high residual stress compared to the layers beneath and the stresses were only equi-biaxial for only up to a few millimetre fractions below the surface. Furthermore, it was observed that the residual stresses were generally tensile and/or compressive in nature at all positions on both gross and net weight on the produced alloy in as-cast conditions. MAGMASOFT method could only predict the, surface residual stresses and the predicted residual stress results are under estimated and/or under predicted. This resulted inconclusive conclusions to be made. Since, only 2 castings were tested for residual stress measurement using HDM. In addition, the magnitude of the residual stresses would depend on the casting section thickness and the effect of unwanted material from net-shape casting component induces either tensile stresses or compressive stresses, depending on the proximity of region being investigated. It is suggested that further work be carried out to reach conclusive results.
M.Tech. (Metallurgy)