铁基合金激光熔覆层的高温磨损性能

 为提高40Cr钢表面耐磨性,采用预置激光熔覆法在40Cr基体表面制备Fe基涂层,利用HT-500摩擦磨损实验机测定干摩擦条件下,基体和熔覆层的摩擦因数随温度变化的规律。利用表面粗糙度轮廓仪测量磨痕的深度和宽度,SEM观察熔覆层以及磨痕的显微组织形貌,使用HV-1000型显微硬度仪检测基体和熔覆层结合部分的硬度。研究结果表明:熔覆层平均显微硬度值达到373.8HV(0.2);显著高于基体硬度198.4HV(0.2)。在干摩擦条件下,随着温度升高,磨损过程逐渐变平缓,平均摩擦因数降低,磨损率增加,耐磨性下降;在350~400 ℃之间,熔覆层磨损性能优于基体。     

激光熔覆NiCrBSi涂层组织及摩擦磨损性能

采用激光熔覆技术在H13钢表面制备了NiCrBSi合金涂层,利用OM,SEM,EDX和XRD等对熔覆层的微观组织进行了分析,测试了熔覆层的显微硬度和摩擦磨损性能。结果表明,激光熔覆层与基体形成了良好的冶金结合,熔覆层的组织主要由γ-Ni,Cr7C3和CrB等相组成。熔覆层显微硬度在650~850HV之间,明显高于H13钢基体的硬度。摩擦磨损实验表明,在相同的条件下,熔覆层的耐磨性比基体有了明显的提高,磨损体积减少了92.4%。通过对磨损后的试样进行粗糙度测试后表明,涂层具有更平滑的表面。     

斜齿轮激光熔覆Fe基合金组织与性能研究

采用激光熔覆技术在斜齿轮钢表面制备Fe基熔覆层。通过光学显微镜、显微硬度计对熔覆层进行金相组织与显微硬度分析,采用磨损机对熔覆层和基材进行摩擦实验。结果表明:当激光功率为750W,送粉速率为20g/min,扫描速度10mm/s,离焦量为16.4mm时,铁基熔覆层与基体结合界面有明显的白亮带,激光熔覆效果较好,熔覆层的显微硬度值分布在845.3HV至955.6HV之间,约为基体硬度(419.7HV)2倍;熔覆层摩擦磨损性能得到了提高;熔覆层显微组织为均匀而细小的铁素体和珠光体,力学性能优于基体材质。     

激光熔覆TiC陶瓷涂层的组织和摩擦磨损性能研究

采用激光熔覆技术在TC4合金表面上制备了TiC陶瓷涂层,分析了熔覆层的微观组织,测试了熔覆层的硬度和摩擦磨损性能。结果表明:TiC激光熔覆层分为熔覆区和稀释区两个区域,熔覆区未受到基底的稀释,由TiC颗粒和TiC树枝晶组成;稀释区受到了基底的稀释,由TiC树枝晶和钛合金组成;TiC激光熔覆层的显微硬度在HV700~1500之间,明显地改善了TC4合金表面的摩擦和磨损性能。     

钛合金表面激光熔覆TiC_p/Ni基合金复合耐磨涂层

采用激光熔覆技术在TC4合金表面制备TiC颗粒增强的Ni基合金复合材料涂层,测试了熔覆层的硬度和滑动摩擦磨损性能,分析了熔覆层的强化机制。结果表明,熔覆层中存在颗粒强化、固溶强化和细晶强化等多种强化作用,熔覆层的显微硬度达HV900～1100,耐磨性能比TC4合金显著提高。     

40Cr钢表面激光熔覆层的磨损性能

 为研究模具钢熔覆层的磨损性能,采用铁基粉在40Cr钢表面进行激光熔覆,以激光熔覆层为上试样,GCr15钢珠为下试样,采用HT－500磨损试验机进行摩擦磨损试验,并与40Cr基体的磨损性能相对比。利用表面形貌仪测量磨痕深度和宽度。研究结果表明：载荷小于250 g时,相同载荷下基体的摩擦系数大。载荷小于300 g时,随磨损时间延长,熔覆层、基体的摩擦系数都随着载荷增加而减小。当载荷为300 g时,基体的摩擦系数在0.563～0.589之间变化,平均值为0.576,且随时间逐渐升高,耐磨性变差;熔覆层的磨擦系数在0.431～0.457之间变化,平均摩擦系数为0.444,磨痕深度和宽度分别是0.65 mm和1.096 μm,且随时间逐渐下降,表现了良好的耐磨性能。当载荷增加到500 g时,平均摩擦系数和磨痕深度比300 g时分别增加了75％和47倍,且摩擦系数逐渐升高,磨损性能下降。     

稀土CeO_2对镍基纳米Al_2O_3激光熔覆复合涂层组织和性能的影响

采用激光熔覆技术在45钢基体上制备了不同CeO2含量的镍基纳米Al2O3复合涂层,对熔覆层进行了微观组织分析和显微硬度测试。结果表明,随着CeO2含量的增加,熔覆层组织由亚共晶向共晶组织转变;加入1.0%CeO2对镍基纳米Al2O3熔覆层的组织起到明显的细化和净化作用,枝晶生长的方向性减弱,组织趋向均匀,熔覆涂层的显微硬度值比未加稀土的涂层提高了60-95HV0.2。     

激光熔覆TiC-Ni复合涂层的摩擦磨损性能和磨损机制研究

利用光学显微镜和扫描电镜观察了钛合金表面TiC-Ni激光熔覆层的宏观形貌和微观组织,测试了激光熔覆层的硬度、摩擦系数和磨损量。利用SEM观察了磨损的表面形貌和磨屑的形貌,分析了激光熔覆层的磨损机制。结果表明:激光熔覆层组织致密,无气孔和裂纹,硬度为基材的3倍;激光熔覆层的摩擦系数随环境压力的降低而提高,磨损量随环境压力的降低、法向载荷的增加而增加;低载时为轻微的磨粒磨损,高载时为严重的剥层磨损。     

Cr对TiC-VC增强铁基熔覆层耐蚀性及耐磨性的影响

通过X射线衍射、扫描电子显微镜、能谱仪、极化曲线和磨粒磨损实验分析,研究了不同Cr加入量对TiC-VC增强铁基激光熔覆层耐蚀性和耐磨性能的影响。结果表明:熔覆层中物相主要为α-Fe,TiC,VC和TiVC2。随着Cr加入量的增加,伴随有残余奥氏体及Cr3C2的出现,且Cr3C2呈长条状部分聚集、部分单独分布。熔覆层的耐蚀性与耐磨性随Cr加入量的增加呈现先增加后降低的趋势。熔覆粉末中加入适量的Cr元素能显著提高熔覆层的硬度与耐蚀性。当添加质量分数为3.0%的Cr时,熔覆层硬度高达1090HV0.2,且相同磨损条件下熔覆层磨损失重仅约为Q235钢的1/26;当添加质量分数为9.0%的Cr时,所得熔覆层的耐蚀性最好,约为不添加Cr时的3.26倍。     

TiN对Co基合金激光熔覆层组织与性能的影响

采用5 kW CO2激光器在低碳钢表面熔覆Co基合金涂层及TiN/Co基合金复合涂层,研究了两种涂层的组织、显微硬度以及滑动磨损性能。结果表明,Co基合金涂层主要组成相为-γCo,-εCo,Cr23C6等,TiN/Co基合金复合涂层组成相为-γCo,-εCo,Cr23C6,TiN和TiC等。Co基合金涂层由发达的-γCo枝晶和其间共晶组织所组成,TiN/Co基合金涂层典型组织为等轴固溶体以及细小的共晶组织。TiN对熔覆层的组织有显著的改善作用,促使其组织细化,树枝晶向等轴晶转化,同时可显著提高Co基合金涂层的显微硬度及耐磨性能。     

H13钢激光熔覆Co基涂层组织及热疲劳性能

针对热作模具用H13钢工况下易产生热疲劳失效的问题,采用Nd:YAG激光器在H13钢表面制备Co基合金涂层。利用光学显微镜、扫描电镜、能谱仪和X射线衍射仪,对涂层组织、合金元素分布及物相组成进行检测。利用显微硬度计和热震实验法,测试热疲劳对Co基合金涂层和淬火回火态H13钢硬度影响。结果表明,Co基合金涂层从底部到表层,依次为平面晶、胞状晶、树枝晶和等轴晶。Co基合金涂层物相主要由-Co和M23C6相组成,热疲劳后涂层表面形成M2O3和M3O4(M=Fe,Co,Cr)氧化物。Co基合金涂层硬度最高可达706HV0.2且呈梯度降低;热循环1000次后,Co基合金涂层表面硬度降低24.4%,H13钢表面硬度降低37.7%,Co基合金涂层硬度下降幅度低于H13钢。热循环1000次后,Co基合金涂层表面未发现明显热裂纹,H13钢表面形成大量网状热裂纹。Co基合金涂层中,Cr元素形成致密Cr2O3氧化膜使其热疲劳性能优于H13钢。     

Microstructure and dry-sliding wear resistance of PTA clad (Cr, Fe)7C3/γ-Fe ceramal composite coating

A wear resistant (Cr, Fe)₇C₃/γ-Fe ceramal composite coating was fabricated on substrate of a 0.45%C carbon steel by plasma transferred arc (PTA) cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness and dry-sliding wear resistance of the coating were evaluated. Results shown that the plasma transferred arc clad ceramal composite coating has a rapidly solidified microstructure consisting of blocky primary (Cr, Fe)₇C₃ and the inter-blocky (Cr, Fe)₇C₃/γ-Fe eutectics and is metallurgically bonded to the 0.45%C carbon steel substrate. The ceramal composite coating has high hardness and excellent wear resistance under dry sliding wear test condition.     

Microstructure and wear properties of TiCN/Ti coatings on titanium alloy by laser cladding

Titanium carbide nitride (TiCN) reinforced Ti coating was fabricated on the surface of Ti–6Al–4V alloy by laser cladding method. Microstructure and wear properties at the surface of the coating in atmosphere were investigated. Three zones can be distinguished of the coating: the clad zone (CZ), the heat affected zone (HAZ) and the substrate. The clad zone is composed of TiCN dendrites, TiO₂ and Ti. A metallurgical bonding between the coating and the substrate was obtained. The microhardness and wear resistance of the TiCN/Ti coating are significantly improved. The average hardness of the coating is about 3 to 6 times of that of the substrate. The friction coefficients of the substrate and the coating are 0.48 and 0.34 respectively. The friction coefficient of the Ti–6Al–4V substrate was insensitive to the normal load, while that of the cladded TiCN/Ti coating was very sensitive to the normal load. The wear mass losses of the cladded samples are much lower than that of the substrate whatever the normal load is.     

Effects of Ta on microstructure and microhardness of Ni based laser clad coating

Through addition of Tantalum, fine TaC particles were in situ synthesized in a NiCrBSi alloy laser clad composite coating. Microstructure, microhardness and abrasive wear resistance of the composite coating were investigated. The result showed that TaC particles were dispersed in Ni based alloy composite coating, refining the microstructure of the coating after laser cladding. Amount of coarse primary carbides such as M7C3 and eutectic of γ-Ni + M23C6 substantially decreased because the formation of TaC particles suppressed the formation of M7C3 and M23C6. On the one hand, fine TaC particles acted as hard phase, which improved the microhardness of the composite coating; on the other hand, a decrease in amount of the coarse M7C3 and eutectic of γ-Ni + M23C6 reduced the crack susceptibility of the Ni based composite coating. Also, Ta element improved the abrasive wear resistance of the Ni based coating.     

Electrodeposition and tribological properties of Ni-SrSO4 composite coatings

Ni-SrSO₄ composite coatings were electrodeposited on superalloy Inconel 718 from a Watts electrolyte containing a SrSO₄ suspension. Ni-SrSO₄ coatings were investigated by scanning electron microscope, microhardness tester, and friction and wear tester in sliding against a bearing steel ball under unlubricated condition. The incorporation of SrSO₄ into Ni matrix increases the microhardness of electrodeposited coatings. Ni-SrSO₄ composite coating exhibits a distinctly low friction coefficient and a small wear rate as contrasted with pure Ni coating and the substrate. The effect of SrSO₄ particles on microstructure and tribological properties of Ni-SrSO₄ composite coatings is discussed.     

Composite ceramic-Ni60 coating fabricated via supersonic plasma spraying

Using the supersonic plasma spraying (SPS) technique, a composite ceramic-Ni60 coating was prepared on a 45# steel substrate. The particle morphology, coating morphology, and phase structure of the coating were analyzed via scanning electron microscopy and X-ray diffraction. Moreover, the tribological properties of the coating were determined via friction and wear experiments. The results revealed that: the crystal structure of the SPS-produced coating is composed of six phase-structure types, and the coating structure was dense with low porosity. During the wear test (rotation speed of ball: 300 rpm, load: 50 N), the friction coefficient decreased by 32.75%, and the coating underwent abrasive wear (wear mechanism).