钴基复合粉末等离子堆焊层组织与性能的研究

发布时间：2018-02-01 11:01

本文关键词： 钴基合金等离子堆焊 WC 显微组织耐磨性　出处：《山东大学》2017年硕士论文　论文类型：学位论文

【摘要】：阀门是化工、机械等行业中应用很广泛的流体控制设备,由于密封面间受到力的作用相互摩擦和剪切,以及流体的冲刷和腐蚀作用,在使用过程中处在较高温度和较高的流体压力下,阀门极易受到损伤。钴基合金具有优良的耐高温、耐磨及耐蚀性能,是修复和强化阀门密封面的一种重要的材料。本文采用等离子堆焊技术,选用Co-Mo-Cr系、Co-Cr-W系、Co-Cr-Ni系三种不同系列的钴基合金作为堆焊材料,分别在这三种钴基合金中加入一定量的WC颗粒,在304不锈钢表面制备钴基复合粉末堆焊层,研究WC对不同系列钴基合金堆焊层组织和性能的影响。试验表明三种钴基合金等离子堆焊的最佳工艺参数分别为:Co-Mo-Cr系钴基合金,焊接电流99A,送粉量35g/min;Co-Cr-W系钴基合金,焊接电流90A,送粉量35g/min;Co-Cr-Ni系钴基合金,焊接电流99A,送粉量38g/min。钴基合金堆焊层组织主要分为四部分,从堆焊层底部往上分别为熔合区、近熔合区等轴状枝晶、近熔合区与近表面之间有一定方向的粗大的柱状晶和近表面细小的等轴晶。Co-Mo-Cr系钴基合金加入WC后,对组织形态产生较大影响。随WC加入量的增多,在钴基固溶体中析出的碳化物的数量增多,尺寸变大,同时碳化物的形状也发生了变化,由不规则的块状变为十字花状和"X"形;堆焊层的稀释率变大。加入 10%WC 时,堆焊层由 y-Co、CoSi、Co7Mo6、CrSi2、CoWSi、Mo3Co3C、M23C6等组成;随WC加入量增多,基体相减少,碳化物相增多,出现Fe3W3C、Fe3Mo3C;加入40%WC时,堆焊层中出现WC相。在Co-Cr-W系钴基合金中加入10%～30%WC后,晶粒变得十分细小,堆焊层先析出枝晶状的钴基固溶体,然后在枝晶间形成共晶组织;当WC的加入量为40%时,熔池中的含碳量较高,析出多种花状碳化物。加入10%WC时,堆焊层是由 γ-Co、CoCx、Cr7C3、CrSi2 组成;加入 20%WC 和 30%WC 时,出现 M6C 型碳化物Co3W3C;WC的加入量为40%时,钴基合金堆焊层的稀释率变大,Fe含量升高,生成Fe3W3C相。在Co-Cr-Ni系钴基合金中加入量为10%～20%WC时,堆焊层的组织类型没有变化,晶粒变细;加入30%WC时,堆焊层上部出现球状组织;当WC为40%时,堆焊层组织出现较大变化,在钴基固溶体中析出花状、块状碳化物。加入10%WC 和 20%WC 时,堆焊层是由γ-Co、Ni-Cr-Fe-C、CrSi2、Co3W3C 组成;加入30%WC时,堆焊层出现Fe3W3C和W2C相。本文采用的三种系列的钴基合金粉末在加入WC后,堆焊层的洛氏硬度和维氏显微硬度都得到较大的提高,并且随WC加入量的增多而增大。在常温磨损试验中,三种系列的钴基合金堆焊层的耐磨性随WC加入量增多而提高,磨损机制随WC加入量增多由磨粒磨损为主转变为黏着磨损和磨粒磨损共同作用。在高温磨损试验中,加入WC颗粒的Co-Mo-Cr系钴基合金堆焊层相比于纯钴基合金堆焊层来说,摩擦系数降低为原来的三分之一。在电化学腐蚀试验中,加入WC后,Co-Mo-Cr系钴基合金堆焊层的自腐蚀电位升高,自腐蚀电流密度大大提高,腐蚀速度加快,使得耐腐蚀性能变差。Co-Cr-W系钴基合金堆焊层加入WC后,自腐蚀电位升高,腐蚀倾向减小,自腐蚀电流密度略有上升,加入10%WC堆焊层的耐蚀性能最好。加入WC后,Co-Cr-Ni系钴基合金堆焊层的自腐蚀电流密度大大降低,加入30%WC堆焊层的耐蚀性最好。
[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.

【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG455

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