Study of the interfacial phenomena during friction surfacing of mild steel with tool steel and inconel

Friction surfacing was carried out with tool steel (AISI 01) and inconel 600 consumables on mild steel 1020 substrate in an argon atmosphere. Inconel bonded strongly with the substrate and there was evidence of interfacial compound formation between the substrate and coating. For tool steel coatings, a sharp boundary between the substrate and coating was observed by scanning electron microscopy. X-ray fluoroscopic imaging also revealed this boundary. Mechanical interlocking between the coating and the substrate appears to be insignificant so adhesion between the coatings and the substrate may be caused by solid-phase bonding. For friction surfacing of both tool steel and inconel, a nominal contact pressure as high as 21.8 MPa was required to obtain an adherent coating of uniform quality. © 1998 Chapman & Hall     

Mechanical, microstructural and oxidation properties of reactively sputtered thin CrN coatings on steel

Thin (40 nm and 160 nm) CrN coatings were deposited on steel by reactive magnetron sputtering deposition, varying the N₂ flow. The coatings were characterized in the as-deposited condition and after annealing in air at 500 °C for 1 h, by X-Ray Diffraction, Transmission Electron Microscopy, Raman and Fourier Transform Infrared spectroscopies. Hardness was measured by nanoindentation. Coatings have a nanocrystalline microstructure with the phase shifting from Cr₂N to CrN, increasing grain size, thermal stability and resistance to oxidation with increasing N₂. Also intrinsic coating hardness is influenced by both N₂ flow during deposition and film thickness, as a result of changes in phase composition and microstructural properties.     

Design of Polymer Coatings in Automotive Engines

Driven by economical and ecological reasons, thermoplastics based coatings were more and more used in automotive engines. Two design concepts, flame spraying and serigraphy PEEK coatings on light metal substrate, were introduced in this paper. The friction and wear behavior of PEEK based coatings were investigated systematically. Coatings with different crystallinities can be obtained when cooling speed is controlled. Among three sprayed coatings considered with different crystallinities, the one with highest crystallinity exhibits best friction and wear behavior under dry sliding condition. Under lubricated sliding condition, however, the amorphous coating gives lower friction coefficient. The micron particles such as SiC,MoS2 and graphite in composite coatings can improve significantly the coating wear resistance and have a impact on coating friction behavior.     

Synthesis of Boride Coating on Steel using High Energy Density Processes: Comparative Study of Evolution of Microstructure

Ultrahard titanium diboride (TiB₂) coatings are deposited on plain carbon steel substrate using two high energy density processes, viz. pulsed electrode surfacing (PES) and laser surface engineering (LSE). These two processes are entirely different in physical nature and hence result in dissimilar microstructures. In the present investigation, a comparative study has been made between the evolved microstructures. Both processes produced a surface layer which is adherent and metallurgically bonded to the substrate. PES produced relatively thinner and less uniform coating than LSE process. The PES coating was, however, homogeneous and very fine grained. The laser-assisted coating was “composite” in nature with TiB₂ particles embedded in Fe matrix. Mechanical characterization of these coatings has been performed using microhardness measurements.     

等离子熔覆铁基涂层的组织及冲蚀磨损研究

采用等离子熔覆法制备了铁基涂层.研究了涂层的组织结构,测试了涂层的显微硬度及耐冲蚀磨损性能,并利用扫描电镜对涂层显微组织、冲蚀表面形貌进行了分析.结果表明:涂层显微硬度是基体材料不锈钢1Cr18Ni9Ti的2倍,最高达到550,涂层冲蚀后质量损失是不锈钢对比试样1Cr18Ni9Ti和0Cr13Ni5Mo的1/2左右.     

Characteristics and performance of hard Ni60 alloy coating produced with supersonic laser deposition technique

A novel coating fabrication technique, known as supersonic laser deposition (SLD), which combines cold spray (CS) with laser technology, is applied to produce hard Ni60 (58–62 HRC) coating on medium carbon steel (AISI 1045 steel) substrate. Different process parameters are investigated to obtain the optimal. The Ni60 coating specimens prepared by SLD process are studied microstructurally using scanning electron microscope (SEM), energy dispersive spectrum (EDS) and X-ray diffraction (XRD). The microstructures of the coatings are compared with those of the coatings produced using laser cladding (LC). The hardness, tribological property and corrosion resistance of the Ni60 coatings produced by SLD and LC with the optimal process parameters are evaluated under Vickers hardness, pin-on-disk wear and electrochemical corrosion tests. It is demonstrated that the Ni60 coating with SLD exhibits some characteristics, such as fine microstructure as cast, stable phases and less dilution; it surpasses the coating produced with conventional LC process in sliding wear resistance; but in 1 mol/L H₂SO₄ solution, the SLD and LC coatings performed similarly in corrosion resistance. This research has proved that SLD technique enables depositing hard Ni60 on steel substrate, which is impossible for CS technique.     

Structure and mechanical properties of PVD coatings deposited onto the X40CrMoV5-1 hot work tool steel substrate

This work presents the research results on the structure and mechanical properties of coatings deposited by PVD methods on the X40CrMoV5-1 hot work tool steel substrates. The tests were carried out on CrAlSiN, CrAlSiN+DLC, CrN and WC/a-C:H coatings. It was found that tested coatings have nanostructural character with fine crystallites, while their average size fitted within the range 3-13 nm, depending on the coating type. The coatings demonstrated a dense cross-sectional morphology as well as good adhesion to the substrate, the latter not only being the effect of interatomic and intermolecular interactions, but also by the transition zone between the coating and the substrate, developed as a result of diffusion that caused mixing of the elements in the interface zone and the compression stresses values. The critical load L_C2 lies within the range 45-55 N, depending on the coating type. The coatings demonstrate a high hardness (4000 HV).     

Effect of cryogenic treatment on microstructure, mechanical and wear behaviors of AISI H13 hot work tool steel

This paper focuses on the effects of low temperature (subzero) treatments on microstructure and mechanical properties of H13 hot work tool steel. Cryogenic treatment at −72 °C and deep cryogenic treatment at −196 °C were applied and it was found that by applying the subzero treatments, the retained austenite was transformed to martensite. As the temperature was decreased more retained austenite was transformed to martensite and it also led to smaller and more uniform martensite laths distributed in the microstructure. The deep cryogenic treatment also resulted in precipitation of more uniform and very fine carbide particles. The microstructural modification resulted in a significant improvement on the mechanical properties of the H13 tool steel.     

纳米TiC颗粒对Ni-TiC复合镀层组织与性能的影响

采用双脉冲复合电镀技术,在瓦特型镀液中,制备含微-纳米TiC颗粒的Ni基复合镀层。研究镀液中纳米TiC添加量对复合镀层微观形貌、组织结构、硬度、摩擦和抗氧化性能的影响。结果表明:镀液中添加纳米TiC后,Ni-TiC复合镀层表面出现团聚、致密度降低,复合镀层的组织为Ni和TiC;随镀液中纳米TiC添加量的增加,复合镀层的显微硬度呈先增后降的趋势,而摩擦因数则先降后升;当纳米TiC颗粒添加量为6.0g/L时,复合镀层显微硬度最大,为445HV,摩擦因数较小,为0.22,磨损机制以磨料磨损为主;在900℃,100h氧化条件下抗氧化性能最佳,氧化增重为6.828mg/cm~2,为微米复合镀层的0.5倍。     

碳化钛/钛镍金属间化合物复合涂层相组织研究

利用钛粉、镍粉和胶体石墨,真空条件下通过反应钎涂技术在低碳钢基体上制备了与基体冶金结合的碳化钛/钛镍金属间化合物复合涂层。采用扫描电子显微镜、能谱仪、X射线衍射仪及硬度计,研究了涂层的相组成、组织结构和成分分布。涂层组织由NiTi2、NiTi、TiC和hcp Ti组成,而涂层界面由NiTi和少量的hcp Ti构成,并且TiC主要分布在涂层中层。涂层中的NiTi2、NiTi、TiC是在钎涂过程中原位反应合成的,而且TiC和NiTi的量随碳含量的增加而增加。涂层表面硬度达到85HR15N,但不随TiC和NiTi含量增加而增高。     

Application of reaction synthesis principles to thermal spray coatings

Reaction synthesis principles have been extended to plasma spraying to obtain coatings consisting of mixed oxide phases and iron aluminides. Elemental powders of iron and aluminium were fed through a d.c. plasma torch to deposit intermetallic coatings on carbon steel substrates. Carbon steel substrates were also pre-heated with a plasma flame to create an iron oxide surface on the substrate such that an exothermic thermite reaction takes place when molten splats of aluminium impinge the pre-heated substrate at sub- or supersonic velocities. A thermite reaction between iron oxide and aluminium allowed the formation of alumina, FeAl2O4, iron, and iron aluminide phases. The presence of FeAl2O4 and Al2O3 increased the surface hardnesses of the coating, and the hardnesses of the coatings are significantly higher than the hardnesses of steel substrate, and aluminium particles. X-ray analysis of the coatings, microstructural observations, and microhardness measurements suggest that plasma spraying conditions can be tailored to obtain coatings with high hardness values with in situ synthesized reinforcements (spinel and alumina) or iron aluminide phases. Aluminium-rich phases were observed in the as-deposited coatings when a mixture of aluminium and iron or aluminium and nickel were fed through the plasma gun in ratios equivalent to Fe3Al, FeAl, Ni3Al, and NiAl. In some cases, annealing allowed the formation of iron-rich or nickel-rich aluminide phases. High solidification rates of molten splats allowed very limited diffusional reactions between the splats of aluminium and iron, or aluminium and nickel because the available diffusional time for exothermic interfacial reactions is limited to a fraction of a second at best. Oxidation of part of the aluminium led to the formation of alumina in the as-deposited coatings, and therefore, a vacuum plasma spraying technique is desirable to obtain intermetallic phases. The results suggest that reactive spraying will allow deposition of coatings by utilizing the heats of reaction between the constituents, and reactive spraying will broaden the engineering applications of reaction synthesis techniques.     

HVOF sprayed WC–Co coatings: Microstructure,mechanical properties and friction moment prediction

This study aims at gaining a better understanding of the microstructural features that control the mechanical and the tribological performances of WC–12 wt.% Co coatings under High Velocity Oxygen Fuel (HVOF) spraying conditions. This paper looks at the influences of the HVOF process parameters for WC–12Co material on the microstructural and the tribological behaviours of the coatings. The correlation between the coating microstructure and the wear behaviour is investigated by observing and analysing the microstructure and by studying the friction moment using enhanced statistical tool based on neural computations. According to the experimental and the numerical results, it has been shown that the spray parameters affect the phase composition, hardness and porosity of HVOF sprayed WC–12Co coatings and the correlations with HVOF process parameters are fully predictable in the steady-state regime.     

真空熔烧钴基合金--碳化钨复合涂层材料的耐磨性能研究

采用真空熔烧法制得钴基合金——碳化钨复合涂层材料,借助扫描电子显微镜、X射线衍射仪、显微硬度计等先进的测试手段对涂层的组织结构和表面形貌进行观察分析。应用盘销式摩擦磨损试验机对不同碳化钨含量的复合涂层材料和淬火态45钢进行了磨损试验。试验结果表明,在相同试验条件下,复合涂层的耐磨性显著高于淬火钢,且其耐磨性随碳化钨含量的增加而提高,淬火钢的耐磨性随着载荷的增加迅速降低,而复合涂层的耐磨性则变化不大。     

Bias effects on the tribological behavior of cathodic arc evaporated CrTiAlN coatings on AISI 304 stainless steel

In this study, CrTiAlN coatings were deposited on AISI 304 stainless steel by cathodic arc evaporation under a systematic variation of the substrate bias voltage. The coating morphology and properties including surface roughness, adhesion, hardness/elastic modulus (H/E) ratio, and friction behavior were analyzed to evaluate the impact of the substrate bias voltage on the coating microstructure and properties. The results suggest that for an optimized value of the substrate bias voltage, i.e. − 150 V, the CrTiAlN coatings showed increased Cr content and improved properties, such as higher adhesion strength, hardness, and elastic modulus in comparison to the coatings deposited by other substrate bias voltage. Moreover, the optimum coatings achieved a remarkable reduction in the steel friction coefficient from 0.65 to 0.45.     

激光熔覆镍基合金与铝反应合成Ni-Al金属间化合物覆层的研究

以镍基合金和铝为原料,利用激光熔覆技术在低碳钢表面反应合成Ni-Al金属间化合物覆层。采用SEM,EDX,TEM和XRD等表征手段对试样的组织和相结构进行分析。结果表明:激光熔覆镍基合金与铝反应合金覆层由β-Ni Al和γ′-Ni3Al两相构成,两相中均固溶有一定量Fe,Si元素。β-Ni Al相含量较多,为细小、均匀、交错分布的树枝晶,Ni,Al间的反应放热使树枝晶呈现等轴化趋势;γ′-Ni3Al相含量较少,呈连续网状分布于β-Ni Al树枝晶周围,这种结构有利于降低覆层脆性。在1.5kW功率下,激光熔覆镍基合金及铝反应合成的β-Ni Al和γ′-Ni3Al两相合金覆层致密,有少量气孔但无裂纹现象,覆层与基体实现完全冶金结合。     

Rare-earth La2O3 modification of laser-clad coatings

The effect of rare-earth La2O3 on laser-clad coatings has been studied. For this purpose, nickel-based alloy powders with different contents of La2O3 were laser-clad on to a steel substrate. The clad coatings were examined and tested for microstructural features, microhardness, inclusions and phase composition. The results are compared with those for coatings without La2O3. The comparison indicates that additions of La2O3 refine the microstructure of the clad, and the coating increases its microhardness. Moreover, the wear resistance and corrosion resistance of the clad coatings are also enhanced.     

冷作模具钢等离子渗镀CrVN复合涂层摩擦磨损性能研究

采用等离子渗镀技术在DC 53冷作模具钢表面制备CrN和CrVN复合涂层,利用X射线衍射仪(XRD)、X射线光电子能谱(XPS)、扫描电镜(SEM)、显微硬度计和摩擦磨损试验机,对比研究了两种涂层的组织结构、力学性能以及摩擦磨损性能。结果表明:所制备的CrN和CrVN涂层均为面心立方(fcc)结构,并呈现(111)择优取向,其中CrVN涂层形成了以fcc-CrN相为基础的CrVN固溶体结构。CrN涂层中掺入V抑制了柱状晶生长,涂层结构更加致密,硬度和结合力明显提高,摩擦系数及磨损率降低。CrVN涂层表面粗糙度较低,并在摩擦过程中生成具有自润滑性的VO₂,涂层抗粘铝性能得到改善。     

H13钢离子渗氮(PN)与类金刚石(DLC)复合处理的摩擦磨损性能研究

采用阳极层流离子源与非平衡磁控溅射结合的沉积方法在H13钢基体表面沉积出类金刚石膜(DLC),并对H13钢经不同表面预处理对后沉积的DLC膜的摩擦学性能进行了对比研究.结果表明:DLC膜结构致密,且DLC膜与梯度过渡层及基体三者之间结合牢固;H13钢经离子氮化后,梯度过渡层与氮化层间结合紧密,提高了膜与基体的承载能力;在保持相同摩擦速率的条件下,摩擦系数随着载荷的增加先增大后减小;H13钢离子渗氮处理后沉积的DLC膜其摩擦系数远小于未采用离子渗氮处理沉积的DLC薄膜.     

Effect of process parameters on physical measurements of AISI316 stainless steel coating on EN24 in friction surfacing

An investigation was successfully made in the present work to obtain the solid-state coating of AISI316 stainless steel over EN24 medium carbon steel by friction surfacing process. Spindle speed, axial force, and table traverse speed were perceived to be the supreme aspects for bonding integrity. It was observed that the depth of the coating (C_t) lessened as the coating width (C_w) increased. The impact of process parameters on physical geometry of the coating was explored by experimentation based on desirability approach. The coefficients of correlation for coating width (0.94) and thickness (0.99) are extremely high. The coatings exhibited martensitic microstructure with fine grain size and without carbide particles which substantiates the effectiveness of good bonding. The optimal process parameters were identified by response surface methodology as 2.26?mm/s of Ts, 7.20?kN of AL, and 1447.17?rpm of RoS and also the output values are observed as C_t?=?2.10?mm and C_W?=?17.21?mm.     

Untersuchung des tribologisch‐mechanischen Verhaltens amorpher Kohlenstoffschichten mittels Load Scanner

Amorphous carbon coatings have a beneficial tribological behaviour since they provide low friction even under dry sliding conditions and at the same time they offer a good wear protection. Under high loads, the applicability of state‐of‐the‐art amorphous carbon coatings is limited by mechanical failure. However, there is still little knowledge concerning the precise failure mechanisms under application‐oriented conditions. In the present study, cylindrical specimens of a cold work tool steel were coated with two commercial amorphous carbon coating systems: a WCC coating with an a‐C:H:W top layer and a DLC coating which architecture is based on that of the WCC coating, but contains an additional a‐C:H top layer. The coated specimens were tested on a load‐scanning test rig in dry sliding contact against uncoated specimens of the same steel substrate. In the tests, the specimens were loaded with a normal force in the range of 13 and 350 N, corresponding to a maximum contact pressure of 1 to 3 GPa. The number of load cycles was varied between 1 and 60. Firstly, the load‐dependent friction behaviour was monitored. Secondly, the tests were stopped at different total cycle numbers allowing for an evaluation of the progress of wear and damage by scanning electron microscopy. For both coating systems, adhesive pick‐up of counter body steel was observed prior to mechanical failure. Whilst the WCC coating system showed first indications of local failure after several load cycles and at contact pressures exceeding 2 GPa, the DLC coating system showed catastrophic failure on a global scale only after few load cycles and over the whole investigated load range.