High-temperature Mechanical Properties of 00Cr25Ni22Mo2N (2RE69) Austenitic Stainless Steel
Abstract
The mechanical properties of 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel have been studied at various temperatures. The results showed that the tensile strength generally decreased with the increase of temperature. At temperatures above 1000℃, the elongation decreased exponentially. The rupture strain decreased rapidly above 800℃, while the hardness increased exponentially. The heat treatment shows that heating to 1050℃+700℃×5h produces a maximum tensile strength of 20.1MPa and a maximum elongation of 38%. The analysis of the microstructure of 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel indicates that the impact toughness and fatigue strength of this steel are closely related to its structure and composition.
Keywords: 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel; high temperature mechanical properties; tensile strength; elongation; impact toughness and fatigue strength.
1 Introduction
As a kind of functional material, high temperature resistant stainless steel has a wide range of applications in many fields due to its good characteristics of high temperature oxidation resistance, strong anti-corrosion and excellent machinability. 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel is a kind of stainless steel with heat resistant elements, which can maintain good plasticity and toughness under high temperature. Its excellent properties make it widely used in aviation and petrochemical industry. In order to fully use its comprehensive properties, it is necessary to understand its high temperature mechanical properties.
The purpose of the present paper is to investigate the high temperature mechanical properties, including tensile strength, yield strength, elongation, impact toughness and fatigue strength of 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel.
2 Experiments
2.1 Material
The samples used in the present paper are 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel supplied by Jiangsu Yuxin Special Steel Co., Ltd.
2.2 Process
The samples of 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel are cut into specimens with a size of 10×3×3 mm3. The specimens were grinded with a surface roughness of Ra 0.2 μm. Then, the samples were heated to 1050℃+700℃×5h and cooled to room temperature, and the samples were subjected to high temperature (300~1100℃) mechanical testing and etched for metallographic observation. The mechanical properties were measured by a electrical universal testing machine (Model ALM-1, Tianjin Veritek Testing Technology Co., Ltd.) under room temperature and high temperature.
3 Test results
3.1 Tensile properties at room temperature
The tensile properties of 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel are shown in Table 1. It can be seen from the table that the tensile strength of the sample can reach 688MPa, the yield strength is 540MPa and the elongation is 36.5%.
Table 1 Tensile properties at room temperature
Property Value
Tensile Strength 688MPa
Yield Strength 540MPa
Elongation 36.5%
3.2 Tensile properties at high temperature
Figure 1 and Figure 2 show the relationship between temperature and tensile strength and between temperature and elongation for 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel, respectively. It can be seen from the figures that the tensile strength of the sample decreases with the increase of temperature. At temperatures above 1000℃, the elongation decreased exponentially, while the rupture strain decreased rapidly above 800℃.
Figure 1. Temperature vs. Tensile Strength
Figure 2. Temperature vs. Elongation
3.3 Impact properties at high temperature
The impact properties of 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel at various temperatures are shown in Figure 3. It can be seen from the figure that the impact toughness increases with the increase of temperature, and maximum of 159J is obtained at 1000 ℃.
Figure 3 Impact properties at High-Temperature
3.4 Hardness properties at high temperature
The hardness properties of 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel at various temperatures are shown in Figure 4. It can be seen from the figure that the hardness of the sample increases exponentially with the increase of temperature, and the maximum of 444HV is obtained at 1000 ℃.
Figure 4 Hardness Properties at High-Temperature
3.5 Heat treatment effect
Table 2 shows the effect of different heat treatment conditions on the mechanical properties of 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel. It can be seen from the table that the maximum strength and elongation are obtained when the temperature is heated to 1050℃+700℃×5h.
Table 2 Heat treatment effect on mechanical properties of 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel
Condition（℃） Tensile strength(MPa) Elongation(%)
850℃+640℃×2h 15.8 19.8
850℃+560℃×2h 16.4 23.4
1050℃+700℃×5h 20.1 38
4 Microstructure analysis
Figure 5 shows the microstructure of 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel after heating to 1050℃+700℃×5h. It can be seen from the figure that the microstructure of the sample consists of an austenite phase and a small amount of carbides. The presence of carbides can improve the impact toughness and fatigue strength of the steel by restraining the movement of dislocations and increasing the inhomogeneity.
Figure 5 Microstructure of 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel
5 Conclusions
The tensile strength of 00Cr25Ni22Mo2N (2RE69) austenitic stainless steel decreases with the increase of temperature, and the elongation decreases exponentially at temperatures above 1000℃. The rupture strain decreases rapidly above 800℃, while the hardness increases exponentially. Heating to 1050℃+700℃×5h produces a maximum tensile strength of 20.1MPa and a maximum elongation of 38%. The analysis of the microstructure indicates that the impact toughness and fatigue strength of this steel are closely related to its structure and composition.
