【摘要】：發(fā)展高參數(shù)超超臨界火電技術(shù)是符合我國(guó)國(guó)情的“潔凈煤發(fā)電”首選技術(shù)。而隨著蒸汽參數(shù)的提高,對(duì)耐熱材料的要求也更加苛刻。葉片作為火電設(shè)備蒸汽輪機(jī)的關(guān)鍵部件,在蒸汽溫度達(dá)到700℃時(shí),葉片材料需要采用鎳基耐熱合金。Waspaloy合金是700-℃超超臨界蒸汽輪機(jī)葉片的主要候選材料之一,本文利用光學(xué)顯微鏡、SEM、TEM、XRD等測(cè)試方法,對(duì)Waspaloy合金的熱變形行為、熱處理制度的影響、700-C長(zhǎng)期時(shí)效過(guò)程中組織與性能變化、持久斷裂壽命進(jìn)行了系統(tǒng)研究；并對(duì)Waspaloy合金的成分進(jìn)行了優(yōu)化,同時(shí)進(jìn)行一定的成分改進(jìn)。取得的主要結(jié)果如下：研究了Waspaloy合金在0.01S-1-l0.0S-1及1000℃～1200℃變形條件下的熱變形行為,建立了合金的熱變形方程以及Z參數(shù)與峰值應(yīng)力間的定量關(guān)系,求得了合金平均激活能為430.9kJ/mol。基于動(dòng)態(tài)材料模型,建立了Waspaloy合金的熱加工圖,并確定了合金最佳的熱加工工藝為：應(yīng)變溫度1050℃到1150℃,應(yīng)變速率為O.O1s-1～0.1s-1時(shí),在此條件下能量耗散率最高能達(dá)到45%,合金能獲得均勻等軸的完全再結(jié)晶組織；而在應(yīng)變溫度1000℃～1050℃,應(yīng)變速率為1.0 s-1～10.0 s-1加工時(shí),會(huì)出現(xiàn)絕熱變形帶,發(fā)生流變失穩(wěn)現(xiàn)象。研究了熱處理制度對(duì)Waspaloy合金組織與性能的影響,隨著固溶溫度的升高,合金強(qiáng)度不斷下降,晶粒尺寸不斷長(zhǎng)大：當(dāng)固溶溫度小于1080℃時(shí),晶粒尺寸可以滿足ASTM標(biāo)準(zhǔn)要求；固溶保溫時(shí)間達(dá)到4h后,合金中僅有少量塊狀MC型碳化物未溶。在845℃進(jìn)行高溫時(shí)效時(shí),合金強(qiáng)度達(dá)到最高,M23C6型碳化物大量析出,并沿晶界呈顆粒鏈狀分布。合金在760℃時(shí)效16h時(shí),合金的強(qiáng)度達(dá)到峰值。得到700℃葉片材料用Waspaloy合金的適宜熱處理制度為1080℃保溫4h,油冷+845℃保溫4h,空冷+760℃保溫16h,空冷。研究了Waspaloy合金在700℃條件下時(shí)效10000h過(guò)程中組織與性能變化。合金主要析出相為富Cr的M23C6型碳化物、富Ti的MC型碳化物和γ’相以及微量的M6C相,時(shí)效過(guò)程中沒(méi)有其他相析出,合金表現(xiàn)出良好的組織穩(wěn)定性。丫'相為球狀顆粒在晶內(nèi)彌散析出,顆粒大小符合正態(tài)分布規(guī)律；丫'相長(zhǎng)大過(guò)程符合Ostward熟化規(guī)律,時(shí)效10000h后γ'相的平均尺寸長(zhǎng)大并不明顯。M23C6型碳化物主要沿晶界析出,隨時(shí)效時(shí)間的延長(zhǎng),其形貌特征經(jīng)歷了由細(xì)小顆粒斷續(xù)分布演變到長(zhǎng)條狀連續(xù)分布,并逐漸長(zhǎng)大的演變過(guò)程。合金中一次MC相會(huì)與基體發(fā)生MC+γ→M23C6+γ'分解反應(yīng),但分解反應(yīng)非常緩慢。在時(shí)效初期,持續(xù)析出丫'相的使得合金的強(qiáng)度明顯提高；當(dāng)時(shí)效時(shí)間超過(guò)2000h以后,丫'相的長(zhǎng)大又會(huì)導(dǎo)致合金強(qiáng)度的緩慢下降。對(duì)合金中C、Ti元素含量進(jìn)行了優(yōu)化研究。合金中C元素的提高能有效增加合金中碳化物數(shù)量,增強(qiáng)碳化物對(duì)晶界釘扎作用,使得晶粒明顯細(xì)化,但對(duì)碳化物種類、分布以及γ'相的形貌特征沒(méi)有明顯影響,不會(huì)改變Waspaloy合金中析出相的種類；當(dāng)C含量取0.016%時(shí),合金強(qiáng)度以及短時(shí)持久性能較低；當(dāng)C取0.056%～0.096%時(shí),合金具有較好的短時(shí)與外推長(zhǎng)時(shí)持久性能。合金中Ti元素的提高不會(huì)引起Waspaloy合金中析出相種類的變化,能有效增加合金中γ'相的數(shù)量,改善合金強(qiáng)度和短時(shí)持久性能,但長(zhǎng)時(shí)外推持久強(qiáng)度會(huì)有所降低；當(dāng)Ti含量為3.18%,合金具有較好強(qiáng)度性能與較好的長(zhǎng)時(shí)外推持久壽命。研究了W元素在Waspaloy合金中的作用。結(jié)果表明在合金中添加2%質(zhì)量分?jǐn)?shù)的W元素,能有效細(xì)化合金中γ'相的尺寸,顯著降低γ'相的長(zhǎng)大速率,改善合金的強(qiáng)度性能、沖擊韌性以及持久性能,不會(huì)改變Waspaloy合金中析出相的種類,在長(zhǎng)期時(shí)效過(guò)程中保持了良好的組織穩(wěn)定性。W元素主要分布于基體和γ'相中,同時(shí)起到固溶強(qiáng)化和沉淀強(qiáng)化作用；添加到合金中的W元素,能夠增加合金中重合位置點(diǎn)陣∑=3晶界數(shù)量,降低晶界界面能量,強(qiáng)化晶界,能同時(shí)改善合金的短時(shí)以及長(zhǎng)時(shí)外推持久性能。700℃下10萬(wàn)小時(shí)持久強(qiáng)度外推值達(dá)到271MPa,比成分改進(jìn)前的Waspaloy合金持久外推性能提高了14.0%。
[Abstract]:The development of ultra-supercritical thermal power technology with high parameters is the preferred technology for clean coal power generation in line with China's national conditions. With the improvement of steam parameters, the requirements for heat-resistant materials are more stringent. LOY alloy is one of the main candidates for ultra-supercritical steam turbine blades at 700-C. In this paper, the thermal deformation behavior of Waspaloy alloy, the effect of heat treatment regime, the change of microstructure and properties during long-term aging and the rupture life of Waspaloy alloy are studied systematically by means of optical microscope, SEM, TEM and XRD. The main results are as follows: The hot deformation behavior of Waspaloy alloy under deformation conditions of 0.01S-1-l0.0S-1 and 1000 ~1200 ~C was studied, the hot deformation equation and the quantitative relationship between Z parameter and peak stress were established, and the average activation of the alloy was obtained. Based on the dynamic material model, the hot working diagram of Waspaloy alloy is established. The optimum hot working process is determined as follows: when the strain temperature is 1050 1150 C and the strain rate is 0.O1s-1 0.1s-1, the maximum energy dissipation rate can reach 45%, and the homogeneous equiaxed fully recrystallized microstructure can be obtained. The effect of heat treatment on the microstructure and properties of Waspaloy alloy was studied. With the increase of solution temperature, the strength of Waspaloy alloy decreased and the grain size grew continuously. The strength of the alloy reaches its maximum at 845 C and M23C6 carbides precipitate in large quantities and distribute along the grain boundaries in a chain shape. The strength of the alloy reaches its peak at 760 C for 16 h. The optimum heat treatment regime of Waspaloy alloy for blade material at 700 C is 1080 C for 4 h, oil cooled 845 C for 4 h, air cooled 760 C for 16 h and air cooled. The microstructure and properties of Waspaloy alloy during aging at 700 C for 10000 h are studied. In addition, no other phases were precipitated in the aging process and the alloy exhibited good microstructure stability. The spherical particles in the Ya'phase dispersed in the grains and the size of the particles accorded with the normal distribution law. The growth process of the Ya'phase accorded with the Ostward aging law, and the average size of the gamma'phase did not grow up obviously after aging for 10000 hours. C-carbide precipitates mainly along grain boundaries, and the morphology of C-carbide evolves from discontinuous distribution of fine particles to continuous distribution of long strips and gradually grows up with the time of aging. The content of C and Ti in the alloy was optimized. The increase of C in the alloy can effectively increase the amount of carbide in the alloy, enhance the pinning effect of carbide on grain boundary and make the grain clear. The results show that the strength and short-term rupture properties of the alloy are lower when C content is 0.016%, and the alloy has better short-term and long-term rupture properties when C content is 0.056%-0.096%. The increase of Ti content will not cause the change of precipitated phase types in Waspaloy alloy. It can effectively increase the amount of gamma'phase in the alloy, improve the strength and short-term rupture properties of the alloy, but the long-term extrapolated rupture strength will be reduced. When the content of Ti is 3.18%, the alloy has better strength properties and long-term extrapolated rupture life. The results show that the addition of 2% W in the alloy can effectively refine the size of the gamma'phase, significantly reduce the growth rate of the gamma' phase, improve the strength, impact toughness and rupture properties of the alloy, and do not change the type of precipitates in the Waspaloy alloy, and maintain good properties during long-term aging. The W element mainly distributes in the matrix and the gamma'phase, and plays the role of solution strengthening and precipitation strengthening. The W element added to the alloy can increase the number of lattice_=3 grain boundaries in the overlapping position, reduce the energy of grain boundaries, strengthen grain boundaries, and improve the short-term and long-term extrapolated rupture properties of the alloy. The extrapolation value of tensile strength reached 271 MPa at 100 000 hours, which was 14.0% higher than that of Waspaloy alloy before composition improvement.
【學(xué)位授予單位】：昆明理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TM621;TG132.3

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本文編號(hào)：2231132