Ni-Fe-Cr合金在固溶處理中的組織變化及其對性能的影響

Ni-Fe-Cr合金在固溶處理中的組織變化及其對性能的影響Microstructure Evolution during Solution Treatment and Its Effect on the Properties of Ni-Fe-Cr Alloy

采用OM和SEM研究了不同C含量Ni-Fe-Cr合金在950~1050 ℃溫度范圍內(nèi)固溶后的組織變化及其對拉伸性能和晶間腐蝕性能的影響。結(jié)果表明，C含量的變化影響固溶處理過程中碳化物的回溶行為和晶粒尺寸，從而造成不同C含量合金力學性能和晶間腐蝕性能的差異。C含量為0.010% (質(zhì)量分數(shù))時，950 ℃固溶處理可使熱加工過程中產(chǎn)生的M23C6碳化物完全回溶，并獲得平均晶粒尺寸約38 μm的等軸晶組織。C含量增加到0.026%時，固溶溫度提高至1000 ℃可使M23C6碳化物完全回溶，獲得平均晶粒尺寸約42 μm的等軸晶組織。C含量在0.010%~0.026%范圍內(nèi)，合金具有較低的晶間腐蝕敏感性，隨C含量增加合金的強度升高，延伸率基本沒有變化。C含量為0.056%時，1050 ℃固溶處理后，局部區(qū)域仍存在未回溶的碳化物，碳化物阻礙晶界遷移使晶粒長大緩慢，造成晶粒尺寸不均勻。同時，未回溶碳化物的存在使合金的強度略有提高，但延伸率降低；未回溶碳化物造成碳化物/基體界面處貧Cr區(qū)的出現(xiàn)，顯著增加了合金的晶間腐蝕敏感性。

Ni-Fe-Cr alloys have been widely used for petrochemical, chemical and nuclear application due to their superior corrosion resistance and good workability. Nowaday, Ni-Fe-Cr alloys with higher strength are demanded for the engineering application. Increasing the carbon content could enhance the strength of Ni-Fe-Cr alloys due to the solid-solution strengthening effect of interstitutial carbon atoms. However, an increase in the carbon content would promote the precipitation of carbides, which reduced the corrosion resistance. In order to optimize the carbon content and determine the solution treatment, microstructure evolution during solution treatment and its effects on the properties of the Ni-Fe-Cr alloys with different carbon content were investigated using OM and SEM. The results show that variation in carbon content affects the carbide dissolution and grain size during solution treatment, which affects the mechanical properties and intergranular corrosion susceptibility of Ni-Fe-Cr alloys. For the Ni-Fe-Cr alloy with carbon content of 0.010wt%, M23C6 carbides produced during the hot-working processes do not exist after solution treatment at 950℃. For the Ni-Fe-Cr alloy with carbon content of 0.026wt%, M23C6 carbides are dissolved into the matrix when the solution temperature increases to 1000 ℃. An increase in the carbon content from 0.010wt% to 0.026wt% results in an increased tensile strength and has little observable effect on the elongation. The alloys with the carbon content in the range of 0.010-0.026wt% have lower intergranular corrosion susceptibility. As the carbon content increases to 0.056wt%, M23C6 carbides could not be dissolved even at the solution temperature of 1050℃, and inhomogenous grain-size distribution is observed. The presence of undissolved M23C6 carbide reduces the solid-solution strengthening effect of carbon atoms, and significantly increases the susceptibility to intergranular corrosion.

全文下載：https://pan.baidu.com/s/1kVgR2Cn