爆炸喷涂Cr_3C_2/25NiCr涂层抗微动磨损性能的研究

研究爆炸喷涂Cr3C2 2 5NiCr涂层的抗微动磨损性能。结果表明 ,爆炸喷涂Cr3C2 2 5NiCr涂层的层间氧化物含量和孔隙率低 ,组织致密 ,结合强度高 ,涂层的抗接触疲劳性能得到有效改善 ,抗微动磨损能力比K417镍基合金和等离子喷涂层显著提高。     

高速火焰喷涂Fe-Al/Cr3C2复合涂层的摩擦学特性

运用高速火焰喷涂方法，选用自主研发的Fe-Al／CrsC2喷涂材料，在20钢基体上制备了复合涂层。利用XRD分析了涂层的相组成，利用SEM分析了涂层表面以及磨损表面形貌，对涂层进行了EDAX分析，并对涂层的摩擦学特性进行了研究。结果表明：高速火焰喷涂Fe-Al／Cr3C2复合涂层中主要相包括Fe3Al、Cr3C2和α-Fe相，涂层的磨损率随温度的升高而下降，具有很好的抗高温磨损性能。     

爆炸喷涂Cr_3C_2-NiCr涂层及其对2Cr10MoVNbN钢疲劳性能的影响

采用爆炸喷涂方法在2Cr10MoVNbN钢基体表面制备了Cr3C2-NiCr涂层,利用光学显微镜、扫描电镜、X射线衍射仪、能谱仪、显微硬度计、电子拉伸试验机、X射线应力仪、疲劳试验机等分析测试了涂层的缺陷、显微硬度、断裂韧度、结合力、残余应力、疲劳性能等,主要研究了涂层对基体疲劳性能的影响.结果表明:在2Cr10MoVNbN钢基体上采用爆炸喷涂方法制备的Cr3C2-NiCr涂层的孔隙率为0.5%,表面硬度为921 HV,断裂韧度为3.67 Mpa·m1/2,涂层与基体的结合强度为63 Mpa,涂层表面、涂层/基体界面处均处于压应力状态;爆炸喷涂Cr3C3-NiCr涂层明显降低了2Cr10MoVNbN钢基体的疲劳性能,在应力幅小于500 Mpa时,与基体试样相比,涂层试样的疲劳寿命减少了75%以上,疲劳强度下降了134.7 Mpa,涂层试样的疲劳裂纹源出现在涂层/基体界面的Al2O3夹杂物处.     

NiCr-Cr_2O_3-BaF_2/CaF_2爆炸喷涂涂层干滑动摩擦磨损性能

在SRV高温摩擦磨损试验机上,考察了25℃和500℃时NiCr-Cr2O3-BaF2/CaF2爆炸喷涂复合涂层与Si3N4球配对时的干滑动摩擦磨损特性。采用FEIQUANTA-600型环境扫描电镜分析了涂层磨损表面形貌,探讨了该爆炸喷涂层的磨损机制。结果表明:500℃时在干滑动摩擦条件下,爆炸喷涂NiCr-Cr2O3-BaF2/CaF2复合涂层表面形成润滑转移膜,显示出优异的高温自润滑性能,与25℃时相比,500℃时涂层的摩擦因数降低了72.2%,磨痕宽度减少了46.6%;温度显著影响涂层的磨损机制,25℃下为黏着磨损,500℃下为严重塑性变形和轻微磨粒磨损。     

大气等离子喷涂工艺参数对Cr2O3涂层磨损性能的影响

通过正交试验分析了大气等离子喷涂中经常需要调整的工艺参数,即电弧电流、氩气流量、氢气流量和喷涂距离对Cr2O3涂层磨损性能的影响,并进行了磨痕的显微形貌观察和能谱分析.结果表明:影响涂层磨损性能由大到小的参数顺序依次为喷涂距离L、氢气流量GH2、电弧电流Ⅰ、氩气流量Gar;随Ⅰ、Gar、L的增大,涂层磨损量先减小后增加;随H2的增大,涂层磨损量减小;最佳工艺参数为电弧电流650 A,氩气流量40 L·min-1,氢气流量10 L·min-1,喷涂距离100mm;Cr2O3涂层的磨损机理为微观断裂剥落和粘着磨损共同作用.     

高速电弧喷涂铁基Cr3C2复合涂层的显微组织

采用高速电弧喷涂技术将自制的铁基Cr3C2粉芯丝材在20钢上制备复合涂层,采用SEM、TEM、XRD等研究了涂层的显微组织和物相结构。结果表明：涂层与基体结合紧密,具有致密的层状结构,颗粒扁平细小,孔隙率低,具有较高的显微硬度;在涂层中存在着多种结构复杂的组织和化合物相,其中α-Fe为基体相,主要硬质相为（Fe,Cr）23C6、（Fe,Cr）7C3,另外还有FeCr2O4、Cr2O3等氧化物相,其中某些物相之间存在着平行的晶体学取向关系。     

瓦楞辊表面等离子喷涂Cr2O3涂层性能研究

利用等离子喷涂技术在瓦楞辊材料42CrMo合金钢表面涂镀Cr2O3硬质涂层,以期提高材料表面耐磨性能.用显微硬度仪测试涂层的硬度,用MFT-4000型高速往复摩擦磨损试验机对涂层进行耐磨性能试验.并用扫描电镜(SEM)、X光衍射仪(XRD)分析了涂层的截面形貌和相结构.结果表明:等离子喷涂Cr2O3涂层后试样表面硬度达到HV1 184.1,试样表面摩擦因数减小,抗磨损性能大幅提高.     

等离子喷涂Cr3C2/MoS2复合自润滑涂层的摩擦学性能

等离子喷涂工艺作为一种表面强化方法,已广泛应用于耐磨、减摩、耐蚀和耐高温等功能涂层的制备.采用等离子喷涂技术,在Q235钢表面制备Cr3C2和Cr3C2/MoS2复合自润滑涂层.对涂层的耐磨特性进行摩擦磨损实验研究,测定显微硬度,并分析涂层的微观结构和物相组成.结果表明,Cr3C2及Cr3C2/MoS2复合涂层的表面硬度平均提高近9倍;在室温干摩擦条件下,Cr3C2型喷涂层的抗磨性能比Q235基体有大幅度提高,加入一定量的MoS2即可维持Cr3C2型涂层的高硬度和抗磨损性能,又可有效降低摩擦因数.     

超音速火焰喷涂WC-10Co-4Cr和CoCrW涂层的微动磨损特性研究

为提高Inconel690合金管的耐磨性,在Inconel690合金管外表面,采用超音速火焰喷涂技术(HVOF)制备WC-10Co-4Cr和Co Cr W两种涂层,管状试样与1Cr13圆柱体配副件以"十"字交叉接触方式,位移幅值为100~200μm;法向载荷为30~90 N;频率为2 Hz;循环次数为3×104次;环境温度为室温,在PLINT微动磨损试验机上进行微动磨损试验。试验结果表明:载荷一定时,涂层的摩擦系数随着位移的增加而变大。两种涂层的耐磨性均显著优于Inconel690合金;WC-10Co-4Cr涂层的耐磨性略优于Co Cr W涂层。清洗后的磨痕表面存在剥落坑和剥层现象,两种涂层的磨损机制主要是剥层和磨粒磨损为主。     

25CrNi2MoV钢的微动磨损性能

采用微动摩擦磨损试验机在干摩擦条件下对新型高速重载传动轴用25CrNi2MoV钢进行微动磨损试验,研究了不同载荷(50~200N)和频率(15~30Hz)下该钢的微动磨损性能。结果表明:在频率为20Hz条件下,当载荷由50N增至200N时,25CrNi2MoV钢的平均摩擦因数由0.766减至0.661,磨损体积由19.65×10^-3 mm^3增至75.83×10^-3 mm^3;在载荷为30N条件下,当频率由15Hz增至30Hz时,平均摩擦因数由0.790增至0.905,磨损体积由11.43×10^-3 mm^3增至23.88×10^-3 mm^3;在不同试验参数下,25CrNi2MoV钢磨损表面均出现了氧化和犁沟现象,磨损机制包含氧化磨损和磨粒磨损;在频率为20Hz条件下,载荷为50,100N时,25CrNi2MoV钢的磨损机制以黏着磨损为主,载荷为150,200N时,主要磨损机制为疲劳磨损;在载荷为30N条件下,频率为15~25Hz时,磨损机制以磨粒磨损为主,当频率增至30Hz时,磨损机制以疲劳磨损为主。     

Tribological properties of plasma sprayed and laser remelted 75/25 Cr3C2/NiCr coatings

A CO₂ laser was used to fuse based Ni–Cr Cr₃C₂ coatings for the purpose of homogenizing their microstructures and eliminating their porosity. Tests of layer control and wear resistance were carried out on the samples treated with the laser. The results have shown that laser remelting improves the microstructure of the coatings, increases the coating microhardness, and improves coating–substrate adherence. The dry sliding wear behaviour was characterized by the existence of two periods. During the first period the square of the wear volume is proportional to the sliding distance. During the second, the wear volume is proportional to the sliding distance.     

纳米Fe-Al/Cr_3C_2复合涂层及其抗高温腐蚀性能

制备纳米金属间化合物Fe-Al/Cr_3C_2复合涂层并测试其抗腐蚀性能,为利用热喷涂技术治理火电站易损部件腐蚀问题提供有效手段。运用自主研发的造粒系统,成功对高活性的纳米Fe-Al/Cr_3C_2复合喷涂粉体实施团聚造粒;运用高速火焰喷涂方法,在结构材料表面制备出了纳米Fe-Al/Cr_3C_2复合涂层,对比测试了微米、纳米Fe-Al/Cr_3C_2复合涂层的抗高温腐蚀性能,分别采用抛物线型和幂函数型对腐蚀动力学曲线进行拟合。纳米Fe-Al/Cr_3C_2复合喷涂材料的粒径由原始的50nm团聚到最终的114~178μm,团聚后的纳米颗粒呈圆形或椭圆形,各成分比例保持原始比例,团聚颗粒内部仍然保持纳米粉体状态;纳米Fe-Al/Cr_3C_2复合涂层表面致密、铺展均匀,截面元素过渡平缓、层片细小;运用幂函数方程对腐蚀动力学曲线的拟合效果更好。通过对腐蚀动力学拟合方程进行求导运算可推算出各复合涂层的腐蚀速率。团聚后的纳米颗粒满足热喷涂材料的相关要求,纳米Fe-Al/Cr_3C_2复合涂层的抗高温腐蚀性能显著高于微米Fe-Al/Cr_3C_2复合涂层。纳米Al、Cr优先氧化生成具有保护作用的氧化膜机理解释了纳米涂层抗高温腐蚀性能优异的原因。     

Improvement in tribological properties of plasma-sprayed Cr3C2–NiCr coating followed by electroless Ni-based alloy plating

Electroless-plated Ni-based alloy coatings, Ni, Ni–Co and Ni–Mo coatings with thickness less than 5 μm were deposited on surfaces of plasma-sprayed Cr₃C₂–NiCr coating. The tribological properties of these electroless-plated coatings against the as-sprayed Cr₃C₂–NiCr coating as sliding pairs were investigated with a block-on-ring arrangement in air at room temperature. It was found that all the Ni-based alloy coatings effectively improved the tribological properties of the Cr₃C₂–NiCr coating. Especially when the Cr₃C₂–NiCr coatings plated with Ni–Co and Ni–Mo coatings were against the as-sprayed Cr₃C₂–NiCr coating as sliding pairs, friction coefficients of 0.10 to 0.13 and coefficients wear coefficients less than 10⁻⁶ mm³·N⁻¹·m⁻¹ were achieved. Through examination and analysis of the worn surfaces employing scanning electron microscopy and X-ray photoelectron spectrometer, the improvement in tribological properties of the Cr₃C₂–NiCr coating may be attributed to the transformation of wear mechanism and the formation of CrO₃ on the worn surfaces.     

Effects of anti-wear additives on friction and wear properties of Cr2O3 coating

The effects of some anti-wear additives on the friction and wear behaviour of plasma-sprayed Cr₂O₃ coating were investigated using a block-on-ring tester at ambient conditions. The results show that zinc dialkyldithiophosphate (ZDDP), tricesyl phosphate (TCP) and tributyl phosphate (TBP) significantly reduce the wear of Cr₂O₃ coating lubricated by paraffin oil. Additive concentrations as well as sliding time have great influence on the wear. The friction coefficient varies slightly with test conditions. The analysis by XPS of worn surfaces indicates that the wear resistance of these additives is due to the formation of tribochemical reaction films by reacting with Cr₂O₃ coatings.     

Impact of Cr3C2/VC addition on the dry sliding friction and wear response of WC–Co cemented carbides

Two grades of WC–10 wt.%Co cemented carbide with or without addition of Cr₃C₂/VC grain growth inhibitor during liquid phase sintering were produced with the goal to investigate their reciprocating sliding friction and wear behaviour against WC–6 wt.%Co cemented carbide under unlubricated conditions. The tribological characteristics were obtained on a Plint TE77 tribometer using distinctive normal contact loads. The generated wear tracks were analyzed by scanning electron microscopy and quantified topographically using surface scanning equipment. The post-mortem obtained wear volumes were compared to the online assessed wear. Correlations between wear volume, wear rate and coefficient of friction on the one hand and sliding distance and microstructural properties on the other hand were determined, revealing a significant influence of Cr₃C₂/VC on the friction characteristics and wear performance.     

Durability of plasma-sprayed Cr3C2-NiCr coatings under rolling contact conditions

The aim of this paper was to address the rolling contact fatigue (RCF) failure mechanisms of plasma-sprayed Cr3C2-NiCr coatings under different tribological conditions of contact stress. Weibull distribution plots of fatigue lives of the coated specimens at different contact stresses were obtained. The failure modes of coatings were identified on the basis of wore surface observations of the failed coatings. Results showed that the RCF failure modes can be classified into four main categories, i.e., surface abrasion, spalling, cohesive delamination, and interfacial delamination. The probabilities of the surface abrasion and spalling type failures were relatively high at low contact stress. When the coatings were subjected to abrasion and spalling type failures, the failure of the coating was depended on the microstrcture of the coating. The stress concentration near the micro-defects in the coating may be the may reason for the formation of spall. The coatings were prone to fail in delamination under higher contact stresses. However, the delamination of coating may be related to distribution of shear stress amplitude within coating. The location of maximum shear stress amplitude can be used as a key parameter to predict the initiation of subsurface cracks within coating in rolling contact.     

Sliding wear characteristics of plasma-sprayed Al2O3 and Cr2O3 coatings against copper alloy under severe conditions

Al₂O₃ and Cr₂O₃ coatings were deposited by atmospheric plasma spraying and their tribological properties dry sliding against copper alloy were evaluated using a block-on-ring configuration at room temperature. It was found that the wear resistance of Al₂O₃ coating was superior to that of the Cr₂O₃ coating under the conditions used in the present study. This mainly attributed to its better thermal conductivity of Al₂O₃ coating, which was considered to effectively facilitate the dissipation of tribological heat and alleviate the reduction of hardness due to the accumulated tribological heat. As for the Al₂O₃ coating, the wear mechanism was plastic deformation along with some micro-abrasion and fatigue-induced brittle fracture, while the failure of Cr₂O₃ coating was predominantly the crack propagation-induced detachment of transferred films and splats spallation.     

Study on rotational fretting wear of bonded MoS2 solid lubricant coating prepared on medium carbon steel

The rotational fretting wear behaviors of the bonded MoS₂ solid lubricant coating and its substrate steel were comparatively studied under varied angular displacement amplitudes, constant normal load, and rotational speed. Dynamic analysis in combination with microscopic examinations was performed through SEM, EDX, XPS, optical microscope, and surface profilometer. The experimental results showed MoS₂ changed the fretting running regimes of substrate. The friction coefficients of MoS₂ were lower than those of the substrate. For MoS₂, the damage in partial slip regime was very slight. The damage mechanism of the coating in slip regime was main abrasive wear, delamination, and tribo-oxidation.     

Tribological properties of Ni3Al-Cr7C3 composite coating under water lubrication

The tribological properties of Ni₃Al-Cr₇C₃ composite coating under water lubrication were examined by using a ball-on-disc reciprocating tribotester. The effects of load and sliding speed on wear rate of the coating were investigated. The worn surface of the coating was analyzed using electron probe microscopy analysis (EPMA) and X-ray photoelectron spectroscopy (XPS). The results show the friction coefficient of the coating is decreased under water lubrication. The wear rate of the coating linearly increases with the load. At high sliding speed, the wear rate of the coating is dramatically increased and a large amount of the counterpart material is transferred to the coating worn surface. The low friction of the coating under water lubrication is due to the oxidizing of the worn surface in the wear. The wear mechanism of the coating is plastic deformation at low normal load and sliding speed. However, the wear mechanism transforms to microfracture and microploughing at high load with low sliding speed, and oxidation wear at high sliding speed. It is concluded that the contribution of the sliding speed to an increase in the coating wear is larger than that of the normal load.