EFFECT OF LASER SCANNING SPEED ON PHASE CONSTITUTION AND WEAR RESISTANCE OF LASER CLADDING HARD FACING ALLOY STELLITE 12

Effect of laser scanning speed on phase constitution,microstructure,microhardness and wear resistance of laser-cladding hard facing alloy Stellite 12 has been investigated by means of a cross-flow-type CO_2 laser of 1.5 kW.The laser-cladding layer on the alloy consists of ma- trix phase of suppersaturated solid solution γ(Co,Cr)and complex hexagonal carbide M_7C_3.Under certain condition,at higher laser scanning speed,the suppersaturated solubility of elements increases in γ(Co,Cr),and the precipitation of the complex carbtde M_7C_3 de- creases,so the microhardness increases and the wear resistance decreases.But at slower laser scanning speed,more complex carbide M_7C_3 may precipitate,and the wear resistance may be improved.Therefore,it is believed that the principal factor in improving wear resistance is the precipitation of carbide M_7C_3,while increment of microhardness is the suppersaturated solu- bility of elements in matrix phase γ(Co,Cr).

Microstructure and wear resistance of electro-thermal explosion sprayed stellite coating used for remanufacturing

Electro-thermal explosion directional spraying was used to prepare the stellite coating on substrate of the AISI 1045 steel. The morphologies of cross-section and worn scar, porosity, distribution of elements, micro- hardness and wear resistance of the coating were determined by means of SEM, EDAX, micro-hardness tester and sliding wear tester. Because of the compact construction, good bonding and high hardness, the coating is characterized by good wear resistance. The results show that the mainly failure mode of the stellite coating is micro- plowing.

激光熔覆Stellite 6合金涂层的耐磨耐蚀性能研究

为提高阀杆用SUS630不锈钢的耐磨耐蚀性能,利用激光熔覆技术在其表面制备Stellite 6钴基合金涂层,随后对比研究了Stellite 6合金涂层和SUS630不锈钢基体的显微硬度、摩擦磨损性能和腐蚀性能。结果表明:相对于SUS630不锈钢,Stellite 6合金涂层的硬度提高了25%,磨损体积减少了50%,说明Stellite 6合金涂层的耐磨性能优于SUS630不锈钢基体;此外,在3.5%NaCl溶液中,Stellite 6合金涂层的腐蚀电位(-0.18 V)和钝化膜的阻抗值(367 kΩcm^(2))均高于SUS630不锈钢基体的腐蚀电位(-0.35 V)和钝化膜的阻抗值(129 kΩcm^(2)),而其钝化电流密度(10^(-7)-10^(-6)A/cm^(2))小于SUS630不锈钢基体的钝化电流密度(10^(-6)-10^(-5)A/cm^(2)),说明Stellite 6合金涂层的耐腐蚀性能优于SUS630不锈钢基体。因此,激光熔覆Stellite 6合金涂层可提高SUS630不锈钢的耐磨耐蚀性能。

HVOF喷涂CoCrWSi和Stellite-6涂层的结构与高温摩擦学性能研究

目的提高F92耐热钢基体在600、630℃下的高温耐磨性能。方法采用超音速火焰喷涂方法(High velocity oxy-fuel,HVOF)在F92表面制备CoCrWSi、Stellite-6两种涂层,利用扫描电子显微镜(Scanning electron microscope,SEM)和X射线衍射仪(X-ray diffraction,XRD)分析涂层的表面、截面形貌和物相组成,通过显微维氏硬度计(HV-1000STA)、高温摩擦磨损试验机(UMT-TRIBOLAB)、二维轮廓仪(TencorD-100)测定其显微硬度、高温摩擦学性能和磨痕体积。结果采用超音速火焰喷涂技术制备的CoCrWSi、Stellite-6两种涂层表面较平整,与基体结合紧密,内部组织均匀无裂纹,涂层的厚度约为200μm。XRD分析表明,CoCrWSi、Stellite-6涂层在室温下的物相都由γ(Co)、Cr_(7)C_(3)、CrSi_(2)组成。硬度及耐磨性能测试显示,CoCrWSi、Stellite-6涂层的维氏硬度相较于F92基体分别提高了3.12、2.68倍,F92耐热钢在600、630℃时的平均摩擦因数分别为0.87、0.86,体积磨损率分别为0.49×10^(-4)、1.11×10^(-4)mm^(3)/(N·m),其磨损机理主要为疲劳磨损、黏着磨损、氧化磨损。相较于基体,CoCrWSi涂层在2种温度下的平均摩擦因数分别降低了68%、71%,约为0.28、0.25,体积磨损率分别降低了约95%、97%,为0.20×10^(-5)、0.30×10^(-5)mm^(3)/(N·m),这主要归功于内部的Cr2O3、γ(Co)、Co_(3)O_(4)相在高温摩擦过程中具有良好的润滑效果。Stellite-6涂层也能在一定程度上改善基体的高温耐磨性能,其平均摩擦因数为0.85、0.71,体积磨损率为0.32×10^(-4)、0.57×10^(-4)mm^(3)/(N·m)。2种涂层的主要磨损机理均为磨粒磨损和黏着磨损。结论采用超音速火焰喷涂制备的CoCrWSi、Stellite-6涂层可以改善F92耐热钢在600、630℃下的耐高温滑动磨损性能,且CoCrWSi涂层的防护效果更佳。

Stellite-6+VC混合粉末激光熔覆性能的研究

小功率脉冲激光下飞机叶片的强化是现在急需解决的问题,本试验通过采用光纤传输300 W Nd:YAG脉冲激光熔覆系统,在低碳钢(SM400B)上熔覆Co基合金(Stellite-6)和碳化钒(VC)混合粉末(VC的质量分数变化范围为0~100%),并对熔覆层的性能进行了研究,从而探究小功率脉冲激光下飞机叶片强化的工艺。试验结果表明,随着VC质量分数的增加,熔覆层组织由亚共晶组织转变为过共晶组织。当VC质量分数小于80%时,熔覆层硬度、裂纹敏感性及耐磨性能随VC增加而增加;当VC质量分数大于80%时,由于母材的稀释作用,熔覆层硬度、裂纹敏感性及耐磨性能随VC增加而降低。试验表明,使用Co基合金(Stellite-6)和碳化钒(VC)混合粉末可以形成耐磨性好、硬度高,裂纹敏感性低的熔覆层,对飞机叶片产生较好的强化效果。

亚微米TiC/B_4C颗粒对激光熔覆Stellite涂层组织及性能影响

通过激光熔覆在304不锈钢表面制备了Stellite 12涂层,研究了添加不同质量分数的Ti/B_4C对Stellite 12涂层组织及性能的影响,分析了涂层组织的生长,测试了涂层的显微硬度及耐磨性能。研究结果表明,Stellite 12涂层主要由面心立方的γ-Co与Cr_7C_3相组成。随着Ti/B_4C的添加,涂层原位合成了TiC亚微米颗粒相。残存的B_4C作为异质形核点,形成了亚微米结构TiC/B_4C强化相,且颗粒尺寸逐渐减小。TiC/B_4C颗粒对涂层晶粒有细化作用。涂层显微硬度随着添加Ti/B_4C的质量分数的增加逐渐增大,最高为624 HV。涂层耐磨性能随添加的Ti/B_4C质量分数的增加逐渐增强。