| With the development of aerospace technology, the high-temperature material in aerospace area has been difficult to meet the requirements. It needs to develop the materials that more stable performance and superior antioxidant performance at a higher temperature. High temperature alloy with nickel based plays an important role in aerospace high-temperature structural parts and enjoy special position in the field of high temperature alloy. So, the development of Ni based alloy material with more stable performance at high temperature is imminent. In view of this, the typical high temperature oxidation mechanism of alloy materials that forming of Cr2O3 or Al2O3 oxide film and the influence of adding active elements on oxidation behavior were studied. Some discussion was made from the optimal sintering process, which to provide some theoretical basis for developing high performance and high temperature materials, further understanding of the mechanism of active elements.In this paper, the powder metallurgy technology was used to prepare Ni based alloys with different content of Al, Cr, Y2O3. The effect of compositions and sintering temperature on ambient temperature mechanical properties and high temperature oxidation resistance of alloys was researched, and its mechanism of action was analyzed. The results show that:1. After sintering, the Ni-5Al-xY2O3 (x=0～1, wt%) alloy was mainly made of Ni phase and the Ni-10Al-xY2O3 (x=0-1, wt%) alloy was mainly consisted of Ni3Al phase, which indicated that adding Al in the alloy would help to Ni and Al combine to form Ni3Al phase.2. With the increase of Y2O3 content when sintering at 1250℃, the hardness and bending strength of Ni-10Al-xY2O3 and Ni-5Al-xY2O3 alloy were decreased, while they were improved with the increase of Al content. The maximum hardness value of the Ni-5Al-xY2O3 Ni-10Al-xY2O3 was 173.1HV and 24.48 HV, respectively, and the minimum hardness value was 101.2HV and 19.85HV. The flexural strength of Ni-10Al-1.0Y2O3 was reduced 669MPa than Ni-10Al, while improved 503MPa than Ni-5Al-1.0Y2O3.3. After Ni-5Al-xY2O3 alloy oxidizing at 1100℃, the oxidation mainly consists of two layers namely outer layer wass NiO, while inner layer was Al2O3, NiAl2O4 or both. The Oxidation resistance of Ni-5Al-xY2O3 alloy was decreased gradually with the increase of Y2O3 content. The addition of Y2O3 could promote the generation of NiO, and the growth rate of NiO was accelerated and grain size was bigger with the increase of concentration of Y2O3.4. The outer layer oxide film of Ni-10Al alloy was NiO, while inner layer oxide film was formed Al2O3, NiAl2O4 or both. The outer layer oxide film of Ni-10Al-0.2Y2O3 and Ni-10Al-1.0Y2O3 alloy was Al2O3, NiAl2O4 or both, while inner layer oxide film was formed Al2O3. Ni-10Al-0.6Y2O3 alloy was generated only a layer oxide film.The addition of Y2O3 promoted the preferred growth of Al2O3, and enhanced adhesion of the oxide film and the matrix, also improved the oxidation resistance of the alloys. The optimal adding value was 0.6wt.%. The oxidation resistance of Ni-10Al-xY2O3 alloy was better than that of Ni-5Al-xY2O3 obviously.5. With the increase of Cr content, the foramina of Ni-10Al-0.6Y2O3-xCr (x=5-20, wt%) alloy was decreased, and the density was increased, the alloy hardness and bending strength were improved. The hardness and bending strength of alloy would be improved through increasing temperature at the reasonable range. The properties of 20wt.%Cr alloy sintered at 1270 ℃ were optimized, its hardness and bending strength was 352HV and 1605MPa, respectively.6. The high temperature oxidation resistance of Ni-10Al-0.6Y2O3-xCr was better with the increase of Cr, which wasbenefit to improve high temperature oxidation resistance of the alloy. The main oxidation of alloy was Al2O3. Under high temperature, the high content of Cr could promote the formation of Al2O3. |
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