Since the directly bonded interface between TiAl alloy and SCM440 includes lots of cracks and generated intermetallic compounds(IMCs) such as TiC, FeTi, and Fe2Ti, the interfacial strength can be significantly reduced. Therefore, in this study, Cu is selected as an insert metal to improve the lower tensile strength of the joint between TiAl alloy and SCM440 during friction welding. As a result, newly formed IMCs, such as Cu2TiAl, CuTiAl, and TiCu2, are found at the interface between TiAl alloy and Cu layer and the thickness of IMCs layers is found to vary with friction time. In addition, to determine the relationship between the thickness of the IMCs and the strength of the welded interfaces, a tensile test was performed using sub-size specimens obtained from the center to the peripheral region of the friction-welded interface. The results are discussed in terms of changes in the IMCs and the underlying deformation mechanism. Finally, it is found that the friction welding process needs to be idealized because IMCs generated between TiAl alloy and Cu act to not only increase the bonding strength but also form an easy path of fracture propagation.

In this study, SCM440 alloys are investigated to research the effect of wear resistance. For this purpose, three wear factors which are friction force, wear loss and coefficient of friction applied to test wear-resistance. For the wear test, ball-on-disk was used to assess the variation of wear characteristics. Lastly, the coefficient of wear was calculated by using the Archard's wear equation in SCM440 alloys. The applied normal load was fixed at 30N in all test. The test results showed that SCM440 alloy's Vickers hardness average value is near 671.4Hv, the friction force is 4.11N through the Ball-on-disk test, the coefficient of friction and the wear loss are 0.431 and 0.080 respectively. Finally, Archard’s wear value of SCM440 alloys could be shown approximately 0.1514.

일반적인 3-전극 시스템의 순환전압전류법을 사용하여 유기부식억제제인 트리에탄올아민 (TEA)을 첨가하여 SCM440 강에 대한 전류-전압 곡선을 측정하였다. 그 결과 SCM440 강의 C-V특성 은 순환전압전류법으로부터 산화전류에 기인한 비가역 공정으로 나타났다. 확산계수는 부식억제제 TEA 의 농도를 2.5 x 10-4 M에서 5,0 x 10-4 M로 2배로 증가시킴에 따라 확산계수는 각각 2.561 x 10-6 cm2s-1에서 1.707 x 10-6 cm2s-1로 1.5배로 감소하므로 부식억제효과가 좋음을 알 수 있었다. 그리고 전 해질 농도변화에 따르는 효과는 전해질 농도를 0.5 N에서 1.0 N로 증가시키면, 확산계수는 각각 5.12 x 10-6 cm2s-1에서 2.56 x 10-6 cm2s-1로 2배로 감소하므로 1.0 N의 전해질의 사용이 적합하였다.

The purpose of this study is to investigate cutting characteristics and wear behavior in SCM440 steel with different cutting tools, CBN(Cubic Boron Nitride) and coated CBN. During the test coated CBN toolespecially with TiAlN showed better wear resistance behavior than orginal CBN tools. In the interruptedcutting condition, axial groove affected tool surface with impact force during the turning operation. Foradvantageous turning parameter in the interrupted process it is recommendable that lower speed. Also surface roughness showed better behavior in the coated CBN tool conditions than normal CBN conditions. Mainly this is caused by reduced friction between material and tool surface with coated layer.

여러 온도에서 급냉 및 템퍼링시킨 SCM440강을 이용하여 결정입도와 조직의 변화가 초음파감쇄에 미치는 영향에 관하여 연구하였다. 초음파감쇄는 주로 결정립에 의한 산란에 기인하였으며 감쇄계수는 결정립의 크기가 클수록 증가하였으나 템퍼링 시킨 조직의 경우 템퍼링온도가 높아질수록 감쇄계수는 감소하는 것을 알 수 있었다. 주파수의 의존성은 직선적인 log-log 관계를 가지며 Roney의 식과 비례하는 것으로 조사되었다.

초음파의 표면파의 전파특성을 이용하여 SCM440강의 고주파열처리의 정도에 따른 표면경화층의 깊이를 측정, 조사하였으며 침탄속도는 동일조직에서는 주파수에 관계없이 일정하였으나, 경화조직에서 경화되지 않은 조직에 비하여 표면파의 속도는 59m/s 늦었다. 강의 유효경화층깊이(d)와 표면파파장(λR)의 d/λR의 관계로부터 경화층의 ?이를 비파괴적으로 평가, 측정할 수 있었으며 침탄경화시킨 경우에서도 동일한 결과를 얻었다.