Kurşunsuz pirinç alaşımların üretimi ve bazı katkı maddelerinin işlenebilirlik, mekanik ve korozyon özelliklerine etkisi

In this study, the effects of MnS and MoS2 additives on the machinability, microstructural, mechanical and corrosion properties of lead-free brass alloys produced by casting method instead of lead alloying element due to the adverse effect of lead on human health were investigated. Commercially available Free-cutting brass (C36000) and Ecobrass alloys were used in production of reference samples. The main alloying elements were melted at the temperature between 1100 and 1150oC. Additives were added into melt pool and stirred with graphite rod to obtain homogenous microstructure in the following step. Finally, molten alloy was poured and solidified into the mould, produced by high speed steel. The microstructures of lead-free brass alloys produced have consisted of alpha, beta and intermetallic compound which was confirmed by the results of X- Ray Diffraction (X-RD) analysis and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS). The microstructure of lead free brass alloys revealed three different morphologies which are Widmanstäetten, dendritic and coarse grains by virtue of solidification parameter, type and content of additives. From the view of phase transformation, the formation of beta phase was promoted by the existence of Si and Sn; in addition, duplex alpha-beta phase transformed to single beta phase in the microstructure with increasing Si content. Hardness value increased with increasing beta phase in microstructure; moreover, the hardness value of the samples was greatly affected by the distribution of phases. The machinability of prepared and reference samples was evaluated in terms of surface roughness and chip formation. Chips obtained from the sample prepared with both MoS2 and MnS additives is of the discontinuous type. In addition, morphologies in microstructure are found to have a great impact on machinability. The surface roughness value of sample prepared with MoS2 additive was found to be the lowest due to its lubricity effect. Corrosion behavior of sample with MoS2 addition were shown to be superior than reference samples. The ultimate tensile strength and elongation of MnS samples are close to limit value according to EN 12164 standards. The wear test results show that the samples produced with the addition of MoS2 have low friction coefficient and high wear resistance due to the lubricant effect of MoS2. Finally, it was determined that the newly developed MoS2-2 sample had the same or similar properties as F.C.B and Ecobrass, which are currently commercially used in industry. In addition, the newly developed brass alloy with the addition of MoS2 proved to be a promising lead-free brass alloy with good corrosion behavior, better wear resistance and low surface roughness, an exceptionally low coefficient of friction and comparable hardness and mechanical properties, and a favorable chip shap