Papers by Author: E. Haruman

Abstract: In this paper, a local/global approach has been used to predict weld induced distortion in butt joint. This approach combines non-linear thermo-elastic plastic and linear elastic analyses to compute final distortion triggered by the welding process. Distortion can lead to dimensional inaccuracy and thus causing the rise in fabrication cost. In this study, Finite Element Method (FEM) software Sysweld and Pam-Assembly were used for computing the welding deformation. The material used for the simulation was low carbon steel with thickness of 4 mm. Based on the result obtained, it was observed that this approach provides fast computation time and efficient solution.

Abstract: This paper describes the results of four thermochemical surface treatments of austenitic stainless steels carried out at 450oC in a fluidised bed furnace and they are nitriding, carburizing and the newly developed hybrid process involving the simultaneous and sequential incorporation of nitrogen and carbon to form a dual layer structure in order to achieve much enhanced surface hardness and wear resistance without compromising the corrosion resistance of the steel. In all these treatments there formed alloyed layers with a common feature of being precipitation-free and supersaturated with nitrogen, or carbon or both in the austenite lattice which is known as S Phase or expanded austenite. However the layer thickness was not uniform in any of these treatments and an effective layer was produced after 8h treatment duration. The nitriding treatment produced thicker and harder layer compared to other treatments; the maximum hardness was over 1500 Hv for nitriding and the minimum hardness of 500 Hv for carburizing treatment. The nitriding treatment sample gave high wear resistance which corresponded to high hardness values.

Abstract: In the present investigation, low temperature nitriding has been attempted on AISI 316L austenitic stainless steel by using a laboratory fluidized bed furnace. The nitriding was performed in temperature range between 400°C and 500°C. X-ray diffraction, metallography, and corrosion tests were used to characterize the resultant nitrided surface and layers. The results showed that fluidized bed process can be used to produce a precipitation-free nitrided layer characterized by the S phase or expanded austenite on austenitic stainless steel at temperatures below 500°C. But there exists a critical temperature and an incubation time for effective nitriding, below which nitriding is ineffective. The corrosion behaviour of the as-nitrided surfaces is significantly different from that previously reported for low temperature plasma nitriding. This anomaly is explained by the formation of iron oxide products and surface contamination during the fluidized process.

Abstract: This paper gives a brief review on the three low temperature plasma surface alloying processes that have been developed in recent years to engineer the surfaces of austenitic stainless steels to achieve much enhanced surface hardness and wear resistance, without compromising their corrosion resistance. These include low temperature plasma nitriding, low temperature plasma carburizing and the newly developed hybrid process involving the simultaneous incorporation of nitrogen and carbon to form a dual layer structure. The processing, structural and property characteristics of each process are discussed briefly in this paper.