热处理工艺对一种新型铸造镍基高温合金的组织和性能影响

EFFECTS OF HEAT TREATMENT PROCESS ON THE MICROSTRUCTURE AND PROPERTIES OF A NEW CAST NICKEL-BASED SUPERALLOY

通过改变固溶热处理温度、保温时间和固溶后冷却方式,研究了不同固溶热处理工艺对一种新型铸造高温合金组织和性能的影响.结果表明,将合金在不同温度固溶处理2 h后空冷,合金在760℃,660 MPa和980℃,180 MPa条件下的持久寿命随热处理温度的升高先升高而后降低;固溶处理温度为1220℃时,760℃,660 MPa条件下的持久寿命达到最高;固溶处理温度为1180℃时,980℃,180 MPa条件下的持久寿命最高;当热处理温度从1120℃升高到1220℃时,拉伸强度随温度升高而增加,继续升温到1240℃,拉伸强度下降.当固溶热处理温度为1120℃,处理时间在2-8 h范围内变化时,合金在760℃,660 MPa条件下的持久寿命随时间延长而降低,而在980℃,180 MPa条件下的持久寿命随处理时间延长而升高;当热处理时间为2和4 h时,拉伸强度较高;延长到6和8 h时,拉伸强度下降.当冷却方式不同时,合金持久性能也发生变化.γ′相和γ/γ′共晶组织在尺寸、形态、分布和数量上的变化是导致合金力学性能变化的关键因素.

A new casting Ni-based superalloy is used in industrial and aircraft turbine because of its high strength and excellent hot corrosion resistance at high temperatures（about 900℃）.The effect of heat treatment process on its microstructure and mechanical properties of the experimental casting Ni-based superalloy was studied in the present investigation in order to improve its application level.The results showed that the stress-rupture lives were changed with the increase of heat treatment temperatures.After solution treated for 2 h,then cooling by air cooling,the stress-rupture life under the conditions of 760℃and 660 MPa was the highest in the case of heat treatment temperature at 1220℃,while under the testing conditions of 980℃and 180 MPa the stress-rupture life was the highest in the case of heat treatment temperature at 1180℃.The stress-rupture life decreased when being heat-treated at temperatures above 1220 or 1180℃.The tensile strength of the alloy was improved with the increase of heat treatment temperatures from 1120 to 1220℃,and was decreased in the case of heat treatment temperature at 1240℃.The experimental results also showed that with the increment of holding time from 2 to 8 h at 1120℃the stress-rupture life increased under the conditions of 760℃and 660 MPa,while it was decreased under the conditions of 980℃and 180 MPa. It was found that the tensile strength was higher for the alloy being held for 2 and 4 h than that for the alloy being held for 6 and 8 h,and the stress-rupture lives changed with the different cooling ways. The mechanical properties of the alloy may be determined by the size,shape,distribution and volume fractions ofγ＇ phase andγ/γ＇ eutectic.