A study on adhesion and wear resistance of VC(vanadium carbide) coating on die steels, STD11 and STD61, has been carried out. The VC coating on the die steels was made by immersing them in molten borax bath, a kind of TRD(thermo-reactive deposition and diffusion). Adhesion strength and wear resistance were investigated using scratch test, indentation test and plate-disc test(Ogoshi type) respectively. The influence of sliding distance on the amount of wear has been determined and dominant wear mechanisms has been characterized using optical microscopy, scanning electron microscopy and EDS spectroscopy. The critical adhesion strength($L_c$) between VC coating layer and substrate(STD11) was increased to 60N($L_c$) in the scratch test. In the case of STD61, the strength increased to 24N. The wear resistance of VC coated die steels was excellent because the diffusion layer formed just below the coating layer. The dominant wear mechanism was identified as adhesive wear for VC coating die steels which were worn by combination of cracking and plucking of VC fragments and disc.

The influence of transformation cycles (${\alpha}^{\prime}{\leftrightarrow}{\gamma}^{\prime}$) on the microstructure and mechanical properties of lath and lenticular martensites has been studied in Fe-Ni alloys. The width of lath in Fe-15%Ni alloy decreased with increasing the number of transformation cycles, while no appreciable change in dislocation density inside the lath was observed. In case of Fe-31%Ni alloy, a number of dislocations were additionally introduced into the martensite plate after the transformation cycling. Tensile strength and Vickers hardness of lath martensite decreased with the increase in number of transformation cycles, whereas those of lenticular martensite increased up to 1 cycle and then remained constant. Elongation of two alloys was deteriorated after 1 transformation cycling, corresponding to the tensile strength. But the decrement of elongation in Fe-31%Ni alloy was smaller than that in Fe-15%Ni alloy.

The structure and mechanical properties of TiN and TiCN thin films deposited on STD61 steel substrates by the RF-sputtering methods has been studied by using XPS, XRD, micro-hardness tester, scratch tester, and wear-resistance tester. XPS results showed that the TiCN thin film formed with chemical bonding state. The TiN thin films grew with (111) orientation having the lowest strain energy by compressive stress, whereas the TiCN thin films grew with both (111) and (200) orientation, but (200) orientation having the lowest surface energy becomes dominant as carbon contents increase. The pre-etching treatment of substrate did not affect on the preferred orientation of thin films, but it played an important role in improving mechanical properties of thin films such as the hardness, adhesion and wear- resistance. Especially, the TiCN thin films showed the superior wear resistances due to high hardness and low friction coefficient compared with TiN thin films.

The effect of vacuum heat treatment in the thermal sprayed ceramics coating on a capstan by either high velocity oxygen fuel(HVOF) or plasma thermal spray process was investigated. The coating materials applied on the capstan were tungsten and chrome carbides. In order to characterize the interface between coating layer and bare materials, hardness, adhesion strength, X-ray diffraction(XRD) and microstructural analysis are conducted. The adhesion strength of the carbide coated materials by HVOF process is over 500MPa compared to those of plasma coating process is 230MPa. In case of the carbide coated materials by HVOF process, the adhesion strength is increased to 15MPa and the porosity is reduced under 5% by vacuum heat treatment for 5 hrs at $1000^{\circ}C$. The XRD results reveal that the increasement is believed due to the phase stabilization of metastable $Cr_3C_2$ phase to stable $Cr_{23}C_6$ phase.

Effect of aging treatment on the microstructures and mechanical properties of 7N01 Al alloy was investigated by differential scanning calorimetry, transmission electron microscopy, microhardness measurement and tensile test. Maximum hardness(125.7Hv) and tensile strength(447.3MPa) were obtained from the specimen aged at $120^{\circ}C$ for 32hrs. The major precipitation hardening phase was confirmed as coherent $MgZn_2({\eta}^{\prime})$ phase. Microhardness changes after peakaged condition showed very large decrease upon increased aging time. This result was attributed to the high transformation rate from coherent ${\eta}^{\prime}$ to incoherent ${\eta}$. It was found that the precipitation sequence of 7N01 Al alloy was GP zone${\rightarrow}$metastable spherical hcp $MgZn_2({\eta}^{\prime}){\rightarrow}$ equilibrium rodlike hcp $MgZn_2({\eta})$.

The effects of heat treatments in Al-Si-Mg alloys on the microstructure and hardness have been investigated by the optical microscope, scanning electron microscope(SEM), and Rockwell hardness tester. The materials of various compositions are melted in a vacuum induction furnace under argon atmosphere. Five different Al alloys are prepared from commercial purity aluminium, magnesium and Al-25Si alloy. Two types of aging treatments are performed: i) Isothermal aging of the specimens at $150^{\circ}C$, $170^{\circ}C$ and $190^{\circ}C$. ii) Pre-aging of the specimens at $60^{\circ}C$, $80^{\circ}C$ and $100^{\circ}C$, and followed by final-aging at $170^{\circ}C$ and $190^{\circ}C$. After the heat treatments, Rockwell hardness are measured with all the specimens.