Recently, Laser surface treatment technologies have been used to improve wear charactenitics and fatigue resistance of metal molding. When the laser beam is irradiated on the surface and laser speed is appropriate, the laser focal position is rapidly heated and the thermal energy of surface penetrates the material after irradiation, finally imbuing it with a new mechanical characteristic by the process of self-quenching. This research estimates the material characteristic after efficient and functional surface treatment using HPDL, which is more efficient than the existing CW Nd:YAG laser heat source. To estimate this, microstructural changes and hardness characteristics of three parts (the surface treatment part, heat affect zone, and parental material) are observed with the change of laser beam speed and surface temperature. Moreover, the depth of the hardened area is observed with the change of the laser beam speed and temperature. From the results of the experiments, it has been shown that the maximum hardness is approximately 788Hv when the heat treatment temperature and the travel speed are $1150^{\circ}$ and 2 mm/sec, respectively.

The precipitates of $L2_1$-type $Ni_2AlHf$ phase in B2-ordered NiAl system has been observed by using transmission electron microscope (TEM). The hardness of as-quenched NiAl-Hf alloys is high due to the larger strengthening. However, age hardening of this alloy is not main effect to increase hardness compared to the large microstructural variations during aging. At the beginning of aging, the $L2_1$-type $Ni_2AlHf$ precipitates keep a lattice coherency with the NiAl matrix. The orientation relationship between the $Ni_2 AlHf$ precipitate and the NiAl matrix is <100>$_{Ni2AlHf}$//<100>$_{NiAl}$, {001}$_{Ni2AlHf}$//{001}$_{NiAl}$. By aging treatment for long time $Ni_2AlHf$ precipitates lost their coherency and change their morphology to the spherical ones surrounded by misfit dislocations. The orientation relationship between the NiAl matrix and the $Ni_2AlHf$ precipitates, however, has been kept even after longer aging time. The lattice misfit between the $Ni_2AlHf$ precipitate and the NiAl matrix has been calculated by the selected electron diffraction patterns, and the spacings of misfit dislocations is about 4.5% at 1173 K.

This paper reports the oxidation mechanism of epitaxial Ni thin films grown on GaN/sapphire(0001) substrates, investigated by real-time x-ray diffraction and scanning electron microscopy. At the initial stage of oxidation process, a thin NiO layer with a thickness of ${\sim}50\;{\AA}$ was formed on top of the Ni films. The growth of such NiO layer was saturated and then served as a passive oxide layer for the further oxidation process. For the second oxidation stage, host Ni atoms diffused out to the surfaces of initially formed NiO layer through the defects running vertically to form NiO grains, while the sites that were occupied by host Ni, became voids. The crystallographic properties of resultant NiO films, such as grain size and mosaic distribution, rely highly on the oxidation temperatures.

The two-step gas nitriding was adopted to increase the depth of surface hardening in 3%Cr-Mo-V steel. The two-step gas nitriding consisted of Step I; $520^{\circ}C{\times}20\;hrs$ and Step II; $550^{\circ}{\times}70\;hrs$. The layer of two-step gas nitriding showed better uniformity and deeper nitriding layer than one-step gas-nitriding layer. The maximum surface hardness showed the value of 850 Hv. The maximum depth of nitrogen permeation showed $750\;{\mu}m$ (350 Hv). X-ray diffraction analysis showed that compound layer was mainly consisted of CrN and $\varepsilon-Fe_3N$ phases. These phases were presumed contributing to surface hardening and wear resistance. However, the corrosion resistance of gas-nitrided Cr-Mo-V steel were not improved in the solution of 1 N HCl and NaOH. Therefore, it is necessary that the continuous study for improvement of corrosion resistance hereafter.

Nickel titanium shape memory alloys (NiTi) have been investigated for applications in the biomedical industry. However, little is known about the influences of surface modifications on the propertise of these alloys. The effect of electropolishing and heat treatments was found to exhibit significant surface roughness. Change of phase was B2, r-phase and B19' by heat treatments. In this study, effect of the electropolishing conditions on surface roughness is investigated in Ni-Ti alloys (Nitinol). Variation in phases with heat treatment temperature is investigated for a Ni-Ti alloy by X-ray diffraction and DSC. Characteristic of the microstructure have been observed by SEM. Surface roughness have been measured by AFM. The results clearly show that significant different in surface property to heat treated at $500^{\circ}C$ (R-phase). $TiO_2$ phases preciritated all of the specimens. It is not good effect of surface roughness because made to surface relief. The surface roughness appears to be important in the property of Ni-Ti alloys for biomedical applications.