This paper aims to verify the reliability of the creep-life assessment regarding the STS304H-Type tube for which the hardness method of H. Tanaka is used. For this purpose, the creep-rupture test and the hardness test were conducted with a new tube and used tubes that were exposed to 96,000 hr under a 650oC condition. The hardness value of the used tubes is higher than that of the new tube by approximately 12 Hv to 15 Hv. This test result was applied to the creep-life assessment of the STS304H-Type for which the H. Tanaka hardness method was used, and the life consumption of the used tubes was evaluated as 13%. The rupture times of the new and used tubes are 802 hr and 707 hr, respectively. The use of the test results as a substitution of the results of the Larson Miller Parameter for a life-assessment tool produced a life-consumption calculation of approximately 12%. Similar results can be confirmed between the Larson Miller Parameter method and the hardness method.

In nowadays, the infrared optics is frequently employed to various fields such as military, aerospace, industry and medical. To develop the infrared optics, special glasses which can transmit infrared wave are required. Ge(Germanium), Si(silicon), and fluoride glasses are typically used for material of the infrared optics. Compared with Ge and Si glasses, fluoride glasses have high transmittance in infrared wavelength range. Additionally, UV(ultraviolet) and visible light can be transmitted through fluoride glasses. There characteristics of fluoride glasses makes it possible to evaluate optical performance with generally used visible testing equipment. In this paper, we used design of experiment to find ultra precision machining characteristic of Ge and fluoride glasses and optimized machining process to obtain required form accuracy of PV(Peak to Valley) 0.2 ㎛.