4. Results

### 4.1 The minimum creep strain rate over a wide range of stress levels for P91 high Cr alloy

The specific value of q = 2 of the modified hyperbolic sine law was obtained through trial and error method. The results are summarily shown in Figure 2, where it is clearly shown that the Xu's modified hyperbolic sine law is the best.

#### 4.2 Creep cavity fracture model

#### 4.2.1 The determination of the creep cavitation coefficients

The obtained creep cavitation coefficients were obtained and shown in Table 3, and their application to predict the cavity probability density size distribution is shown in Figure 3 [12].

Based on the obtained values of creep cavity coefficients, the creep cavity nucleation model, the creep cavity growth model, and creep cavity fracture model

Figure 2. The comparison of the modeling of minimum creep strain rate and stress level [12].


Table 3.

The creep cavitation constants for P91 [12].

#### Figure 3.

The comparison of cavity size probability density function for P91, experimental data from ref [22] and only sample points used [12].

Figure 4. The predicted number of cavity with time.

Figure 5. The predicted cavity growth with time.

Modeling of Creep Deformation and Creep Fracture DOI: http://dx.doi.org/10.5772/intechopen.89009

Figure 6.

The predicted caviated area along grain boundary with time.

Figure 7. The trend of the values of U<sup>0</sup> under different stresses and temperatures [12].

Figure 8. Inverse U<sup>0</sup> and stress level for P91 at 600°C.

are also obtained, respectively. The predicted relationships of the number of cavity, the creep cavity growth, and creep damage variable with time are shown in Figures 4–6, respectively.
