Influence of temperature on the R‐effect for the fatigue crack growth of nickel‐base superalloy GH4169

Abstract

The stress ratio (R) effect, especially at elevated temperatures, is associated with the fatigue crack growth (FCG) prediction in aero-engine hot-end components under complex operation conditions. The FCG experiments with three R were conducted on Ni-based superalloy GH4169 at room temperature (RT), 550 C, and 700 C. The results indicate that the R-effect on the FCG of GH4196 is temperature-dependent. Therefore, efforts were made to identify the R-effect at various temperatures to describe the FCG. The concept of the crack-closure or the two-driving-force was employed to quantify the R-effect considering the temperature influence. Fractographic analyses on the fracture surface were performed to discuss the underlying mechanism responsible for the temperature influence. The study can contribute to the R-dependent FCG modeling at various temperatures.

On the Link between Plastic Wake Induced Crack Closure and the Fatigue Threshold

“…However, test data at both a range of R ratio's and temperatures was needed. As a result the super alloy GH4169 [86], which is the Chinese version of Inconel 718, was chosen.…”

“…To continue this study let us next examine the R = 0.1 and 0.7 da/dN versus ∆K curves presented in [86] for the growth of cracks in the Ni-based supper alloy GH4169 tested at room temperature (RT) and also at 550 • C. (GH4169 is a Chinese developed superalloy that has similar mechanical properties to Inconel 718 (IN718) [86]). The room temperature and 550 • C R = 0.1 and 0.7 da/dN versus ∆K curves are shown in Figure 8.…”

“…GH4169 (a Chinese super alloy that has mechanical properties similar to Inconel 718), ASTM E647 CT specimens that were tested at R = 0.1 and 0.7 at both RT and 550 • C, [86].…”

Experimental study of the strengthening effect: A novel fatigue life prediction method for variable amplitude loads

“…[1][2][3][4] It is important to consider the load interaction in life prediction under variable amplitude loads, and many cumulative damage models have been developed. [5][6][7][8][9][10][11] Depending on the relationship between fatigue damage and cycle life fraction, existing cumulative damage models were divided into linear and nonlinear models. The Palmgren-Miner rule 12 is the earliest linear cumulative damage model, widely used due to its simplicity.…”

“…Operating under variable fatigue loadings, the interaction of variable amplitude loads was found to significantly affect fatigue damage accumulation 1–4 . It is important to consider the load interaction in life prediction under variable amplitude loads, and many cumulative damage models have been developed 5–11 …”