机械合金化Ni-20Cr合金的循环氧化行为

Cyclic Oxidation Behavior of Ni-20Cr Alloy Prepared by Mechanical Alloying

结合XRD、TEM、SEM、OM等表面分析技术,研究机械合金化Ni-20Cr合金在1000℃空气中的循环氧化行为,并与熔炼合金进行比较。结果表明:200h循环氧化后,机械合金化Ni-20Cr合金表面生成Cr2O3氧化膜,且剥落轻微;而熔炼Ni-20Cr合金表面生成由NiO和NiCr2O4组成的氧化膜,且剥落严重,其单位面积失重明显大于机械合金化Ni-20Cr合金。在实验条件下,机械合金化Ni-20Cr合金较熔炼Ni-20Cr合金具有更好地抗循环氧化性能。一方面,晶粒细化促进保护性Cr2O3膜的生成;另一方面,晶粒细化使氧化膜中的热应力减小并可通过扩散蠕变来释放,使氧化膜的粘附性明显提高。

XRD, TEM, SEM and OM techniques are used to investigate the cyclic oxidation behavior of Ni-20Cr alloys prepared by mechanical alloying （MA） and conventional casting （CA） at 1000 ~C in air. It is found that a compact Cr203 scale is formed with a very good adhesion for the mechanically alloying Ni-20Cr alloy, even after a cyclic oxidation at 1000 ~C for 200 h, but a slight scale spallation is observed. For the conventional casting Ni-20Cr alloy, a complex scale of NiO/NiCr204 is formed, and a severe scale spallation is observed with a obvious mass decrease after a cyclic oxidation at 1000 ~C for 200 h. The results show that the MA Ni-20Cr alloy exhibits a better cyclic oxidation resistance than the CA Ni-20Cr alloy owing to the fact that the grain refinement can significantly promote the formation of Cr203 scale and enhance the adhesion to the scale by the thermal stress reduction and release.