發(fā)布時(shí)間：2018-07-21 13:37

【摘要】：Hastelloy C-276合金由于其高溫強(qiáng)度高、耐腐蝕性能好,以及優(yōu)異的耐氧化能力,已經(jīng)被廣泛應(yīng)用于化工、石油、核工業(yè)等領(lǐng)域。近年來(lái)Hastelloy C-276合金成為第四代超臨界水冷堆(SCWR)燃料包殼候選材料之一。面對(duì)嚴(yán)苛的工作環(huán)境,Hastelloy C-276合金需要具備更加優(yōu)良的力學(xué)性能和耐腐蝕性能。如何能夠經(jīng)濟(jì)高效的提高Hastelloy C-276合金的相關(guān)性能,是本課題的主要研究目標(biāo)。材料的晶界分布特征與宏觀性能之間有著至關(guān)重要的聯(lián)系,如力學(xué)性能、耐腐蝕性能、蠕變性能等。“晶界工程”是Watanabe于1984年提出的晶界設(shè)計(jì)與控制這一概念發(fā)展而來(lái)的。材料的屬性可以通過(guò)提高材料中特殊晶界比例(低ΣCSL晶界)進(jìn)行優(yōu)化。大量的科學(xué)研究表明,可以通過(guò)采用形變與熱處理的組合工藝達(dá)到提高材料中特殊晶界比例的目的。對(duì)一些低層錯(cuò)能面心立方金屬(如,鎳基合金、奧氏體不銹鋼、銅合金等)使用晶界工程加工工藝,都能使材料的性能得到大幅度提高。Hastelloy C-276合金也是一種低層錯(cuò)能面心立方金屬,對(duì)Hastelloy C-276合金采用晶界工程的加工工藝,也有可能會(huì)提高其性能。本論文使用光學(xué)顯微鏡、掃描電子顯微鏡、電子背散射衍射(EBSD)等檢測(cè)手段研究了軋制變形和熱處理工藝對(duì)Hastelloy C-276合金晶界特征分布的影響;觀察分析了軋制變形對(duì)Hastelloy C-276合金晶粒度的影響規(guī)律;通過(guò)ASTM G28-A法分析了含有不同比例特殊晶界Hastelloy C-276合金的耐腐蝕性能,并且分析了腐蝕后樣品的晶界及基體析出相。同時(shí)使用萬(wàn)能拉伸實(shí)驗(yàn)機(jī)對(duì)Hastelloy C-276合金在650℃下進(jìn)行了高溫拉伸實(shí)驗(yàn),分析了不同特殊晶界比例Hastelloy C-276合金的斷裂機(jī)制。本文研究得出了得出了以下主要結(jié)論:1.與未經(jīng)晶界工程工藝處理的Hastelloy C-276合金相比,晶界工程能夠提高該合金的低ΣCSL晶界比例。2.Hastelloy C-276合金中特殊晶界比例的提高主要是基于退火孿晶(∑3)的形成。軋制變形量為10%,再在1120℃退火10min可使Hastelloy C-276的特殊晶界比例最高,達(dá)到57.9%。3.晶粒長(zhǎng)大階段并不能使特殊晶界比例提高,過(guò)長(zhǎng)的退火時(shí)間反而會(huì)使特殊晶界比例下降。4.低ΣCSL晶界比例為57.9%的樣品腐蝕速率最低,主要是因?yàn)榈挺睠SL晶界比例較高的樣品形成了尺寸較大的晶粒團(tuán)簇,在一定程度上阻止了腐蝕的進(jìn)行,保護(hù)了基體材料。腐蝕嚴(yán)重的樣品晶界會(huì)有析出相產(chǎn)生,析出相的成分為Ni、Mo和Cr這些Hastelloy C-276的主要組成元素,造成材料成分不均勻,會(huì)加速材料的腐蝕。5.不同晶界特征分布的Hastelloy C-276合金的抗拉強(qiáng)度和屈服強(qiáng)度變化不大,隨著低ΣCSL晶界比例的增加,抗拉強(qiáng)度和屈服強(qiáng)度有小幅度下降,是細(xì)晶強(qiáng)化與孿晶強(qiáng)化共同作用的結(jié)果。不同低ΣCSL晶界比例的Hastelloy C-276合金樣品在高溫下拉伸的斷裂機(jī)制均為微孔聚集型斷裂,斷口形貌主要為深淺不一的等軸狀的韌窩,有較好的高溫延展性。
[Abstract]:Hastelloy C-276 alloy has been widely used in chemical, petroleum and nuclear industry due to its high temperature strength, good corrosion resistance and excellent oxidation resistance. In recent years, Hastelloy C-276 alloy has become one of the candidate materials for the fourth generation supercritical water cooled reactor (SCWR) fuel cladding. Facing the harsh working environment, Hastelloy C-276 alloy needs better mechanical properties and corrosion resistance. How to improve the correlation energy of Hastelloy C-276 alloy economically and efficiently is the main research goal of this paper. The grain boundary distribution is closely related to the macroscopic properties, such as mechanical properties, corrosion resistance, creep properties and so on. Grain boundary engineering was developed by the concept of grain boundary design and control proposed by Watanabe in 1984. The properties of the material can be optimized by increasing the specific grain boundary ratio (low 危 CSL grain boundary). A large number of scientific studies have shown that the proportion of special grain boundaries can be increased by the combination of deformation and heat treatment. The grain boundary engineering process is used for some low stacked error-energy facet cubic metals (such as nickel-based alloys, austenitic stainless steels, copper alloys, etc.). Hastelloy C-276 alloy is also a kind of low layer mission-centered cubic metal. It is possible to improve the properties of Hastelloy C-276 alloy by grain boundary engineering. In this paper, the effects of rolling deformation and heat treatment on the grain boundary characteristic distribution of Hastelloy C-276 alloy were studied by means of optical microscope, scanning electron microscope and electron backscatter diffraction (EBSD). The effect of rolling deformation on the grain size of Hastelloy C-276 alloy was observed and analyzed, and the corrosion resistance of Hastelloy C-276 alloy containing different proportion of special grain boundaries was analyzed by ASTM G28-A method. At the same time, the high temperature tensile test of Hastelloy C-276 alloy at 650 鈩，

本文編號(hào)：2135697