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。     

铁基合金激光熔覆层高温润滑磨损性能

 为提高40Cr合金钢的表面耐磨性,采用预置激光熔覆法在40Cr基体表面制备铁基合金涂层, 利用扫描电镜观察分析熔覆层显微组织形貌,用显微硬度仪测试熔覆层截面显微硬度,用摩擦磨损试验机测定在润滑条件下基体、熔覆层的摩擦系数随温度变化的规律。研究结果表明:熔覆层与基体实现良好冶金结合,熔覆层横截面微观组织呈现平面晶、树枝晶和胞状晶分布;熔覆层硬度值介于617.5~926.6 HV0.2之间,基体硬度介于205.2~278.2 HV0.2之间;在200 ℃以下,熔覆层摩擦系数在磨程中趋于平稳,在0.1附近轻微波动,小于基体平均摩擦系数;当温度超过200 ℃,油膜分解,引发润滑失效,磨损方式向干摩擦转化,磨损机理从微切削磨损主导向粘着磨损、磨粒磨损和氧化磨损复合磨损方式转化。     

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。     

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。     

激光冲击强化H62黄铜摩擦磨损性能研究

采用高能激光束对H62黄铜进行单层和三层激光冲击强化(LSP),研究激光冲击前后微观组织、截面显微硬度以及表面粗糙度的变化,发现激光冲击明显细化了H62黄铜的晶粒,形成纳米结构层,并增加了其显微硬度和表面粗糙度,且显微硬度和表面粗糙度随冲击层数的增加而增大。利用UMT-2摩擦磨损实验机分别对原始试样、LSP试样进行摩擦磨损实验,分析了三种试样的摩擦系数、磨损率和磨痕形貌差异,发现在相同的摩擦条件下,LSP试样的摩擦系数和磨损率均比原始试样小,且随着冲击层数从单层增加到三层,摩擦系数和磨损量变得更小,表明LSP能够提高H62黄铜的耐磨性,多层LSP对H62黄铜耐磨性的提升效果更佳。激光冲击后,试样的磨损机制由以剥层磨损为主转变为以磨粒磨损为主。     

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。     

激光熔凝层组织与摩擦学特性的研究

 为研究激光熔凝层的磨损性能，在灰铸铁材料表面进行激光熔凝。以激光熔凝强化的灰铸铁为上试样，灰铸铁为下试样，模拟活塞环、缸套工作环境，进行标准的SRV快速磨损试验。利用表面形貌仪测量配副双方的磨损深度，扫描电子显微镜观察熔凝层、磨痕形貌。结果表明：激光熔凝层显微组织为先共晶奥氏体分布在共晶基底上的亚共晶，显微硬度变化范围在HV0.2 800～HV0.2 1 200之间。上、下试样磨损深度分别为2.04 mｍ和1.35 mｍ，摩擦系数在0.072 8～0.082 2范围内变化，磨损机制为磨粒磨损。     

激光冲击对E690高强钢激光熔覆修复微观组织的影响

为研究激光冲击对E690高强钢激光熔覆修复层微观组织的影响,选用专用金属粉末对E690高强钢试样预制凹坑进行激光熔覆修复,并使用脉冲激光对激光熔覆层进行冲击强化处理,同时采用扫描电镜、透射电镜和X射线应力分析仪分别对激光冲击前后激光熔覆层的微观组织和表面残余应力进行检测。结果表明:激光熔覆修复后,激光熔覆层组织为等轴晶,熔覆层与E690高强钢基体之间冶金结合良好,其表面残余应力为均匀分布的压应力。经激光冲击后,激光熔覆层截面晶粒得到细化,并观察到大量的形变孪晶,互相平行的孪晶界分割熔覆层粗大晶粒,在激光熔覆层的晶粒细化过程中发挥着重要作用;试样表层位错在{110}滑移面上发生交滑移,在晶界周围形成了位错缠结。经激光冲击后,激光熔覆层冲击区域表面残余压应力数值相较于冲击前提升了1.1倍。     

激光熔覆Al+SiC涂层对镁合金表面耐磨性能的改性

通过脉冲激光器(Nd-YAG)在AZ91D镁合金基底上熔覆Al+SiC粉体。采用扫描电子显微镜、能量色散谱(EDS)和X-射线衍射测定分析熔覆层的显微组织、化学成分和物相组成。研究表明:Al+SiC涂层主要由SiC,β-Mg_(17)Al_(12)及Mg和Al相组成,激光熔覆层与镁合金基底表现出良好的冶金结合。所有样品都具有树枝状结构,且随着SiC质量分数的增大,树枝状和胞状结构的间隔变得更大。熔覆涂层的表面硬度高于基底,并且随着熔覆层中的SiC质量分数的增加而增大,SiC质量分数为40%的熔覆层具有最大的显微硬度,达到180 HV,然而质量分数为10%的熔覆层硬度为136 HV。销盘滑动磨损试验表明,复合涂层中的SiC颗粒和原位合成的Mg_(17)Al_(12)相显著提高了AZ91D镁合金的耐磨损性,其中,SiC质量分数从10%增加到30%过程中磨损体积损失逐渐减少,SiC质量分数在20%~30%时熔覆层具有最好的耐磨性。     

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。     

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.     

Microstructure and wear behaviors of laser clad NiCr/Cr3C2-WS2 high temperature self-lubricating wear-resistant composite coating

The high temperature self-lubricating wear-resistant NiCr/Cr₃C₂-30%WS₂ coating and wear-resistant NiCr/Cr₃C₂ coating were fabricated on 0Cr18Ni9 austenitic stainless steel by laser cladding. Phase constitutions and microstructures were investigated, and the tribological properties were evaluated using a ball-on-disc wear tester under dry sliding condition at room-temperature (17 °C), 300 °C and 600 °C, respectively. Results indicated that the laser clad NiCr/Cr₃C₂ coating consisted of Cr₇C₃ primary phase and γ-(Fe,Ni)/Cr₇C₃ eutectic colony, while the coating added with WS₂ was mainly composed of Cr₇C₃ and (Cr,W)C carbides, with the lubricating WS₂ and CrS sulfides as the minor phases. The wear tests showed that the friction coefficients of two coatings both decrease with the increasing temperature, while the both wear rates increase. The friction coefficient of laser clad NiCr/Cr₃C₂-30%WS₂ is lower than the coating without WS₂ whatever at room-temperature, 300 °C, 600 °C, but its wear rate is only lower at 300 °C. It is considered that the laser clad NiCr/Cr₃C₂-30%WS₂ composite coating has good combination of anti-wear and friction-reducing capabilities at room-temperature up to 300 °C.     

Microstructure and tribological properties of TiAg intermetallic compound coating

TiAg intermetallic compound coating has been in situ synthesized successfully on pure Ti substrate by laser cladding using Ag powder as the precursor. It has been found that the prepared coating mainly comprised TiAg and Ti phases. The high resolution transmission electron microscopy results further conform the existence of TiAg intermetallic compound in the prepared coating. The magnified high resolution transmission electron microscopy images shown that the laser cladding coating contains TiAg nanocrystalline with the size of about 4 nm. Tribological properties of the prepared TiAg intermetallic compound coating were systematically evaluated. It was found that the friction coefficient and wear rate was closely related to the normal load and sliding speed, i.e., the friction coefficient of the prepared TiAg intermetallic compound coating decreased with increasing normal load and sliding speed. The wear rate of the TiAg intermetallic compound coating decreased rapidly with increasing sliding speed, while the wear rate increased as the normal load increased.     

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。     

Laser Cladding of Copper Alloys on Steel

The paper discusses the process of welding copper-based powder on samples of steel 40 Kh by radiation of a continuous CO2 laser. It is shown that the friction coefficients are 0.014–0.021 for samples cladded by a scanning beam, which is lower by a factor of two than for samples of cast bronze. The effect of transverse beam oscillations on the quality and performance of the cladding process is studied. It is shown that, for a beam scanning frequency of 220 Hz, the cladding performance increases by a factor of 1.5.