Assessment of Creep Properties Using Small Punch Test for a 9%Cr-Mo-Co-B Power Plant Steel

Abstract

The present study provides a feasible method to evaluate creep properties for a 9%Cr-Mo-Co-B power plant steel by comparing two sets of data obtained from small punch tests and conventional uniaxial creep tests. The method includes three steps: firstly, conduct a series of small punch tests and conventional creep tests in different load and temperature conditions; secondly, convert the load and central deflection data obtained from the small punch test to stress and strain data; thirdly, determinate the best fit correlation factor by comparing the two sets of data in selected creep models. It is found that two sets of data show a similar trend in stress–rupture time relation, stress–minimum strain rate relation and LMP–stress relation. The correlation factor, ksp, can effectively bridge the gap between the load in small punch test and the stress in conventional creep test. For a high-Cr martensitic heat-resistant steel named as CB2, the ksp value 1.4 can make a good prediction for rupture time, while for minimum creep rate and the Larson–Miller parameter, the ksp value 1.4 will lead a conservative prediction in the low-stress range.

Investigation on the Tensile Properties of Inconel 625 Using Small Punch Test

“…Tensile properties of materials are fundamental parameters when estimating the strength degradation and structural integrity of practical facilities. In recent years, many works have been made to analyze material properties-based on miniaturized specimens [1,2]. Small material requirement means that miniature tests can be applied in mechanical properties analysis during the service lives of components.…”

Martensite Decomposition and Ultrafine Grain Formation during Small Punch Creep Testing of Additively Manufactured Ti64

“…The creep technique was already presented in the good practice guidelines [13] and is further developed in the more recent standard to the small punch methods [14]. The SPCT technique was mainly used for studying the creep properties of power plant steels [8,13,[15][16][17][18][19] and has recently been extended to the study of nickel-based superalloys [20]. Regarding the behaviour of the Ti64 alloy, the small punch technique was used to study yielding in both wrought and AM elaborated materials through SPT testing [21][22][23].…”

An Improved Correlation for the Estimation of the Yield Strength from Small Punch Testing

“…Recently, a European standard was published [6]. Thus far, the SP test has been successfully used to estimate (i) the ductile-tobrittle transition temperature where SP tests at different temperatures are used to derive the SP energy as function of test temperature [1,2,7]; (ii) tensile properties, in particular the yield strength (YS) and ultimate tensile strength (UTS) [8][9][10][11][12]; (iii) fracture and damage parameters [3,13,14]; and (iv) creep properties [15][16][17][18][19][20][21][22]. In the European standard [6], the associated methods are described in informative, non-mandatory annexes.…”