發(fā)布時(shí)間：2018-02-01 11:01

  本文關(guān)鍵詞： 鈷基合金 等離子堆焊 WC 顯微組織 耐磨性　出處：《山東大學(xué)》2017年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：閥門(mén)是化工、機(jī)械等行業(yè)中應(yīng)用很廣泛的流體控制設(shè)備,由于密封面間受到力的作用相互摩擦和剪切,以及流體的沖刷和腐蝕作用,在使用過(guò)程中處在較高溫度和較高的流體壓力下,閥門(mén)極易受到損傷。鈷基合金具有優(yōu)良的耐高溫、耐磨及耐蝕性能,是修復(fù)和強(qiáng)化閥門(mén)密封面的一種重要的材料。本文采用等離子堆焊技術(shù),選用Co-Mo-Cr系、Co-Cr-W系、Co-Cr-Ni系三種不同系列的鈷基合金作為堆焊材料,分別在這三種鈷基合金中加入一定量的WC顆粒,在304不銹鋼表面制備鈷基復(fù)合粉末堆焊層,研究WC對(duì)不同系列鈷基合金堆焊層組織和性能的影響。試驗(yàn)表明三種鈷基合金等離子堆焊的最佳工藝參數(shù)分別為:Co-Mo-Cr系鈷基合金,焊接電流99A,送粉量35g/min;Co-Cr-W系鈷基合金,焊接電流90A,送粉量35g/min;Co-Cr-Ni系鈷基合金,焊接電流99A,送粉量38g/min。鈷基合金堆焊層組織主要分為四部分,從堆焊層底部往上分別為熔合區(qū)、近熔合區(qū)等軸狀枝晶、近熔合區(qū)與近表面之間有一定方向的粗大的柱狀晶和近表面細(xì)小的等軸晶。Co-Mo-Cr系鈷基合金加入WC后,對(duì)組織形態(tài)產(chǎn)生較大影響。隨WC加入量的增多,在鈷基固溶體中析出的碳化物的數(shù)量增多,尺寸變大,同時(shí)碳化物的形狀也發(fā)生了變化,由不規(guī)則的塊狀變?yōu)槭只詈?X"形;堆焊層的稀釋率變大。加入 10%WC 時(shí),堆焊層由 y-Co、CoSi、Co7Mo6、CrSi2、CoWSi、Mo3Co3C、M23C6等組成;隨WC加入量增多,基體相減少,碳化物相增多,出現(xiàn)Fe3W3C、Fe3Mo3C;加入40%WC時(shí),堆焊層中出現(xiàn)WC相。在Co-Cr-W系鈷基合金中加入10%～30%WC后,晶粒變得十分細(xì)小,堆焊層先析出枝晶狀的鈷基固溶體,然后在枝晶間形成共晶組織;當(dāng)WC的加入量為40%時(shí),熔池中的含碳量較高,析出多種花狀碳化物。加入10%WC時(shí),堆焊層是由 γ-Co、CoCx、Cr7C3、CrSi2 組成;加入 20%WC 和 30%WC 時(shí),出現(xiàn) M6C 型碳化物Co3W3C;WC的加入量為40%時(shí),鈷基合金堆焊層的稀釋率變大,Fe含量升高,生成Fe3W3C相。在Co-Cr-Ni系鈷基合金中加入量為10%～20%WC時(shí),堆焊層的組織類(lèi)型沒(méi)有變化,晶粒變細(xì);加入30%WC時(shí),堆焊層上部出現(xiàn)球狀組織;當(dāng)WC為40%時(shí),堆焊層組織出現(xiàn)較大變化,在鈷基固溶體中析出花狀、塊狀碳化物。加入10%WC 和 20%WC 時(shí),堆焊層是由γ-Co、Ni-Cr-Fe-C、CrSi2、Co3W3C 組成;加入30%WC時(shí),堆焊層出現(xiàn)Fe3W3C和W2C相。本文采用的三種系列的鈷基合金粉末在加入WC后,堆焊層的洛氏硬度和維氏顯微硬度都得到較大的提高,并且隨WC加入量的增多而增大。在常溫磨損試驗(yàn)中,三種系列的鈷基合金堆焊層的耐磨性隨WC加入量增多而提高,磨損機(jī)制隨WC加入量增多由磨粒磨損為主轉(zhuǎn)變?yōu)轲ぶp和磨粒磨損共同作用。在高溫磨損試驗(yàn)中,加入WC顆粒的Co-Mo-Cr系鈷基合金堆焊層相比于純鈷基合金堆焊層來(lái)說(shuō),摩擦系數(shù)降低為原來(lái)的三分之一。在電化學(xué)腐蝕試驗(yàn)中,加入WC后,Co-Mo-Cr系鈷基合金堆焊層的自腐蝕電位升高,自腐蝕電流密度大大提高,腐蝕速度加快,使得耐腐蝕性能變差。Co-Cr-W系鈷基合金堆焊層加入WC后,自腐蝕電位升高,腐蝕傾向減小,自腐蝕電流密度略有上升,加入10%WC堆焊層的耐蝕性能最好。加入WC后,Co-Cr-Ni系鈷基合金堆焊層的自腐蝕電流密度大大降低,加入30%WC堆焊層的耐蝕性最好。
[Abstract]:The valve is widely used in chemical, fluid control equipment, machinery and other industries, due to the sealing surface between the force of interaction between friction and shear, and fluid erosion and corrosion in the process of using in high temperature and high fluid pressure, the valve is vulnerable to injury to the cobalt base alloy with high temperature resistance. Excellent, wear and corrosion resistance, is to repair and strengthen the sealing surface of the valve is a kind of important material. This paper adopts plasma arc welding technology, selection of Co-Mo-Cr, Co-Cr-W, Co-Cr-Ni, three different series of cobalt based alloy as welding materials, adding a certain amount of WC particles in these three kinds of cobalt based alloy respectively. And the preparation of cobalt based composite powder surfacing layer on the surface of 304 stainless steel, the effects of WC on different series of cobalt based alloy surfacing layer microstructure and properties. The test shows that the optimum parameters of three kinds of cobalt based alloy plasma surfacing Respectively: Co-Mo-Cr cobalt base alloy, the welding current is 99A, the amount of powder 35g/min; Co-Cr-W cobalt base alloy, the welding current is 90A, the amount of powder 35g/min; Co-Cr-Ni cobalt base alloy powder surfacing welding current 99A, send 38g/min. cobalt base alloy layer is mainly divided into four parts, from the bottom of surfacing layer to respectively the fusion zone near the fusion zone and equiaxed dendrite, equiaxed.Co-Mo-Cr cobalt base alloy columnar crystal and near surface small have a certain direction between near the fusion area and near the surface of the coarse after joining the WC, have great influence on the morphology of WC. With the increase of the amount, the number of in the cobalt based solid solution in the carbide precipitation increased, size, and shape of carbides also changed from irregular block into cross flower shape and the shape of "X"; the rate of dilution of surfacing layer becomes larger. When 10%WC was added, the surfacing layer by y-Co, CoSi, Co7Mo6, CrSi2 CoWSi, Mo3Co3C, M23C. 6 other components; with the addition amount of WC increased, the matrix phase decreases, carbide phase increased, Fe3W3C, Fe3Mo3C; adding 40%WC, WC phase appears in the surfacing layer. Adding 10% ~ 30%WC in Co-Cr-W cobalt based alloy, the grains become very small, the surfacing layer precipitated dendritic cobalt based solid solution then, the eutectic formation in the interdendritic; when the dosage of WC is 40%, with higher carbon content in the weld pool, precipitate a variety of flower shaped carbides. The presence of 10%WC, surfacing layer is composed of CoCx, Cr7C3, -Co gamma, CrSi2; adding 20%WC and 30%WC, M6C type carbide Co3W3C; the dosage of WC is 40%, the dilution of cobalt based alloy surfacing layer rate becomes larger, the content of Fe increased, the formation of Fe3W3C phase in Co-Cr-Ni system. The cobalt based alloy addition is 10% ~ 20%WC, the surfacing layer of tissue types did not change, the grains become fine; the presence of 30%WC, the upper portion of the surfacing layer globular structure; when WC is 40% The structure of the surfacing layer, larger changes in cobalt based solution is precipitated in the flower, blocky carbides join 10%WC and 20%WC, surfacing layer is composed of Ni-Cr-Fe-C, CrSi2, -Co gamma, Co3W3C; the presence of 30%WC, Fe3W3C and W2C surfacing layer. The three series of the cobalt alloy powder after joining WC, surfacing layer hardness and microhardness of Vivtorinox have been greatly improved, and with the amount of WC increased. At room temperature and wear test, the wear resistance of cobalt based alloy surfacing layer three series with the amount of WC increased and improved, the wear mechanism with WC addition increased by abrasive wear transition abrasive wear to adhesive wear and wear tests. At high temperature, Co-Mo-Cr cobalt based alloy surfacing layer of WC particles compared to pure cobalt based alloy surfacing layer, the friction coefficient decreased to 1/3 of the original in the electric. Chemical corrosion test, after joining WC, the corrosion potential increased Co-Mo-Cr welding line cobalt base alloy layer, the corrosion current density is greatly improved, the corrosion rate, corrosion resistance worse.Co-Cr-W cobalt based alloy surfacing layer after joining the WC, increased the corrosion potential, corrosion tendency reduced, corrosion current density adding 10%WC increased slightly, corrosion resistance of the surfacing layer is the best. After joining WC, the corrosion current density is greatly reduced Co-Cr-Ni surfacing cobalt base alloy layer, the corrosion resistance of the surfacing layer joining the 30%WC best.

【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TG455

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