Abstract---Tempering is an important process to produce the martensitic stainless steels having the desired properties. This paper reports the influence of tempering temperature on hardness and impact resistance the modified 410-1Mo steels. The steels samples were prepared by a process sequence of induction melting, hot forging, annealing, hardening and tempering. The tempered steels were subjected to hardness and impact testing. The experimental results showed that the hardness and the impact resistance of the steels depended strongly on tempering temperature and they changed considerably at temperature 600 o C. The secondary hardening appeared at tempering temperature around 400-550 o C. The correlation of impact energy with hardness was found to fit the linear line with negative gradient with increasing of hardness value. The fractured surfaces of the impact test specimens were analyzed using SEM images. Keywords: martensitic stainless steels, steam turbine blades, tempering temperature, hardness, impact resistance I. INTRODUCTION During services the steam turbine blades operate within condition of high stress and high temperature erosive-corrosive environment of steams. The blades are usually made from martensitic stainless steels of 13Cr type (403/410) due to its high strength, high toughness and corrosion resistance [1,2]. However, failures of the blades made from this type of steels were frequently found in the last stage of low pressure blades, particularly due to environmentally assisted craking [3,4,5,6]. Improving mechanical properties and corrosion resistance of the 13Cr type martensitic stainless steels can be accomplished by chemical composition modification and heat treatment.This type of steels should be experienced by proper heat treatment process to achieve the desired mechanical and corrosion properties. A standard heat treatment process subjected to the martensitic stainless steels consists of quenching and tempering which respectively contributes to the final properties of the steels. Quenching this type of steels from high temperature where austenite phase formed and carbide dissolution occured results in microstructure consists of mainly hard and brittle martensite, small amount of retained austenite, and may some carbides exist [7,8]. Tempering process should be accomplished following quenching for reducing hardness to increase ductility and toughness.The 410-1Mo martensitic stainless steels is a modification of 410 type steels recently developed by incorportion about 1%Mo which exhibit higher tensile strength and higher elongation at breaks compared to the standard 410 type steels [9]. The heat treatment response on the properties of this steels are being investigated and a part of the results has been published elsewhere [10]. This work reports the influence of tempering temperature on hardness and charpy impact resistance of the 410-1Mo martensitic stainless steels. Fractographic analysis of impact samples and correlation between hardness and impact resistance are also presented.II. EX...