• MATERIALS

    A COMPARISON OF FRICTION CHARACTERISTICS OF VARIOUS SURFACE TREATED HOT WORK TOOL STEEL

    Machines. Technologies. Materials., Vol. 10 (2016), Issue 12, pg(s) 45-47

    Wear, is one of the most important failure type which reduces the service lifetime and increases the maintenance cost of machines. In addition, wear is directly related with surface properties and friction characteristics. So, researchers focus on various surface treatments to reduce the wear and its cost. Plasma nitriding is one of surface treatment which forms a few hundred micron diffusion zone and a surface inter-metallic phases with moderate surface hardness. PVD coating is another method which ensures ultra-hard and a few micron surface layers. In the present study, AISI H13 hot work tool steel substrate was surface treated with various methods, such as plasma nitriding, PVD coating and duplex treatment. Effects of the treatments on the surface roughness, hardness were investigated. Additionally, microstructural analysis was performed to present the effect of treatments on the surface microstructures. Furthermore, friction characteristics were investigated using ball on disk testing machine and wear tracks were discussed using optical microscopy.

  • TECHNOLOGIES

    THE INFLUENCE OF WELDING TIME ON MECHANICAL PROPERTIES OF RESISTANCE SPOT WELDED TWIP STEEL SHEETS

    Machines. Technologies. Materials., Vol. 10 (2016), Issue 11, pg(s) 19-22

    This paper presents an analysis of the welding time effect on the mechanical properties of resistance spot welded TWIP980 steel sheets. Optical microscopy, microhardness measurements across the welded joints, and tensile shear tests of the joints were conducted to evaluate the quality of the joints. With welding time increasing, a macro expulsion cavity occurred in the FZ. The NS increased with increasing welding time up to 300 ms, and above 300 ms it decreased. On the other hand, the indentation depth increased almost linearly with increasing welding time. The hardness values in FZ and HAZ were lower than that in the BM. The lowest hardness values were observed in the HAZ. However, higher welding time led to higher hardness in HAZ. The tensile shear load, tensile shear deformation and failure energy of the joints increased with increasing welding time, but above 300 or 350 ms, these values decreased.