Wear and fracture toughness of partially stabilized zirconia ceramics under dry friction against steel

The wear of two ceramic materials containing partially stabilized zirconia is studied under unlubricated friction against steel. The first material, with ZrO₂ and 3 mol % Y₂O₃, was obtained by cold isostatic pressing and sintering. The second material, comprising ZrO₂ and 4 mol % Y₂O₃, was fabricated by additional hot isostatic pressing. The samples of both materials were fabricated with high and low values of fracture toughness. The samples with high fracture toughness are found to wear more intensively. This fact can be explained by surface micro-cracking during braking as a result of phase transformations.     

Wear behavior and mechanisms of alumina-based ceramic tools in machining of ferrous and non-ferrous alloys

In this paper, the machining performance and wear mechanisms of two alumina-based ceramic cutting tools (Al₂O₃/TiB₂ and Al₂O₃/TiB₂/SiC_w) in continuous turning of hardened steel and nickel based alloy (Inconel 718) were examined. Results showed that in turning of hardened steel performed under identical conditions, Al₂O₃/TiB₂/SiC_w tool exhibited lower flank wear resistance than that of Al₂O₃/TiB₂ tool, the mechanisms responsible for this were determined to be the strong atom bonding between SiC and Fe, and the whisker pullout from the matrix for Al₂O₃/TiB₂/SiC_w ceramic tool. In continuous turning of Inconel 718, the Al₂O₃/TiB₂/SiC_w tool showed greatly improved flank wear resistance compared to Al₂O₃/TiB₂ tool, adhesion and abrasion wear were found to be the dominant wear mechanisms, the adhesion and diffusion of Ni, and Cr of Inconel 718 to the tool rake face may accelerate the tool wear rates.     

A sustainability comparison between drilling and milling for hole-enlargement in machining of hardened steels

Abstract

Hole-making is one of the most important processes of metal shaping domain. Although, drilling is a commonly used approach to cut holes in metallic parts, the process cannot be completed with the cutting action of one drill bit if the work material is hard and diameter of the hole is large. Usually, a drill having diameter equal to the required diameter of the hole is utilized to enlarge a predrilled hole of a smaller diameter. In this work, we have investigated sustainability of using another method of enlarging a pre-drilled hole, namely side and end milling and compared it with the drilling-based approach. The work material used in the study is a high carbon steel, which is heat-treated to two distinct levels of surface hardness. Besides process type and work material hardness, the other two parameters tested in the investigation are cutting speed and depth of hole. A total of 16 experiments were performed to generate data regarding the sustainability measures, namely hole surface roughness, specific cutting energy and tool wear. Process choice (drilling or milling) for hole-enlargement was found to possess a significant effect on all the measured responses. Analyses carried out on the experimental data revealed that although the drilling-based option led to an immensely better surface finish, the milling-based option performed better with respect to the other measures of economic and environmental sustainability.     

高速铣削AF1410高强度钢的实验研究

高强度钢具有优异的机械性能和广阔的应用,但切削加工较为困难,存在加工效率低,加工表面质量差等问题.以AF1410高强度钢为研究对象,应用高速铣削的加工方法,使用涂层硬质合金刀片,对AF1410高强度钢进行了高速铣削实验,研究分析了在高速切削条件下刀具磨损、切削力、切削温度以及已加工表面粗糙度的变化规律.研究发现以TiC...     

Investigation of mechanical and tribological properties of amorphous diamond-like carbon coatings

We investigated the mechanical and tribological properties of amorphous diamond-like carbon (DLC) coatings deposited on Si(100) by a pulsed bias deposition technique. Tribological studies were performed using a pin-on-disc (POD) apparatus under a normal load of 6.25 N and at 10% relative humidity, with a ruby pin as a slider. Hardness measurements were performed using a nanoindenter and apparent fracture toughness using indentation techniques. We studied the influence of residual stresses on apparent fracture toughness. The data revealed that the thickness, hardness and compressive stress of the coating play different roles in the apparent fracture toughness. Crack initiation is influenced by the thickness and hardness of the coating, whereas crack propagation is influenced by the compressive stress in the film. The apparent fracture toughness of DLC coatings increased with coating hardness.     

Experimental investigations on machinability aspects in finish hard turning of AISI 4340 steel using uncoated and multilayer coated carbide inserts

The present work deals with some machinability studies on flank wear, surface roughness, chip morphology and cutting forces in finish hard turning of AISI 4340 steel using uncoated and multilayer TiN and ZrCN coated carbide inserts at higher cutting speed range. The process has also been justified economically for its effective application in hard turning. Experimental results revealed that multilayer TiN/TiCN/Al₂O₃/TiN coated insert performed better than uncoated and TiN/TiCN/Al₂O₃/ZrCN coated carbide insert being steady growth of flank wear and surface roughness. The tool life for TiN and ZrCN coated carbide inserts was found to be approximately 19 min and 8 min at the extreme cutting conditions tested. Uncoated carbide insert used to cut hardened steel fractured prematurely. Abrasion, chipping and catastrophic failure are the principal wear mechanisms observed during machining. The turning forces (cutting force, thrust force and feed force) are observed to be lower using multilayer coated carbide insert in hard turning compared to uncoated carbide insert. From 1st and 2nd order regression model, 2nd order model explains about 98.3% and 86.3% of the variability of responses (flank wear and surface roughness) in predicting new observations compared to 1st order model and indicates the better fitting of the model with the data for multilayer TiN coated carbide insert. For ZrCN coated carbide insert, 2nd order flank wear model fits well compared to surface roughness model as observed from ANOVA study. The savings in machining costs using multilayer TiN coated insert is 93.4% compared to uncoated carbide and 40% to ZrCN coated carbide inserts respectively in hard machining taking flank wear criteria of 0.3 mm. This shows the economical feasibility of utilizing multilayer TiN coated carbide insert in finish hard turning.     

Effect of densification and TiB2 reinforcement on the wear of molybdenum disilicide

Wear tests were done in a pin‐on‐disc machine by sliding MoSi₂ pins against hard‐steel discs in a normal load range of 5–140 N and a speed of 0.5 m/s under nominally dry conditions in the ambient. The specific wear rate of the pin undergoes two transitions: severe to mild at low load and mild to severe at high load. The mild‐wear domain is distinguished by the formation of a protective mechanically mixed layer of steel and its oxides, transferred from the counterface in particulate form. Increasing the hardness by densification and TiB₂ reinforcement lowers the specific wear rate and expands the mild‐wear load domain. However, even when the volume wear rate is normalised with respect to the real contact area (load/hardness) the non‐dimensional wear factor is still seen to decrease with densification and reinforcement. This indicates that fracture toughness may also play an important role in determining the wear‐resistance of these materials. The surface coverage on the pin by the mechanically mixed layer increases with densification and reinforcement. This revised version was published online in July 2006 with corrections to the Cover Date.     

刀具损坏形式计算机辅助分析系统的开发

设计开发了刀具损坏形式计算机辅助分析系统 (TFP CAAS)。应用该系统可根据刀具损坏形式迅速、准确地查到刀具损坏 (包括磨损和破损 )原因 ,并提出相应的解决方案     

Development of a cutting tool condition monitoring system for high speed turning operation by vibration and strain analysis

Cutting tool wear is a critical phenomenon which influences the quality of the machined part. In this paper, an attempt has been made to create artificial flank wear using the electrical discharge machining (EDM) process to emulate the actual or real flank wear. The tests were conducted using coated carbide inserts, with and without wear on EN-8 steel, and the acquired data were used to develop artificial neural networks model. Empirical models have been developed using analysis of variance (ANOVA). In order to analyze the response of the system, experiments were carried out for various cutting speeds, depths of cut and feed rates. To increase the confidence limit and reliability of the experimental data, full factorial experimental design (135 experiments) has been carried out. Vibration and strain data during the cutting process are recorded using two accelerometers and one strain gauge bridge. Power spectral analysis was carried out to test the level of significance through regression analysis. Experimental results were analyzed with respect to various depths of cut, feed rates and cutting speeds.     

Ni基、Ni-W基涂层刀片加工高强度钢的切削性能研究

用新研制的Ni基、Ni W基涂层刀片与未涂层刀片进行了高强度合金钢的对比车削试验和切削性能研究 ,结果表明 ,新型涂层刀片切削性能良好 ,磨损较小 ,耐用度提高。通过适当研磨Ni基涂层刀片的前刀面 ,可有效提高刀片涂层的抗剥落能力     

Development of a novel cubic boron nitride cutting tool with a textured flank face for high-speed machining of Inconel 718

Nickel-based superalloys such as Inconel 718 offer several advantages, including high-temperature strength and high corrosion resistance; this has led to a rapid increase in the demand for such materials, particularly in the aircraft industry. In contrast, these alloys are known to be among the most difficult-to-cut materials because of their mechanical and chemical properties, and tools used for this purpose have extremely short lifetimes. Recently, cubic boron nitride (CBN), which is the second hardest of all known materials, has received significant attention as a material for cutting tools and has already established itself in many fields of application. However, the performance of CBN tools is still insufficient for practical use, especially in the high-speed machining of Inconel 718. To overcome this problem, we first conducted orthogonal cutting experiments on Inconel 718 and performed cross-sectional observations of the CBN cutting tool in order to identify its wear mechanisms in continuous cutting operations under high-speed machining conditions (300 m/min). As a result, it was found that fatal tool failure occurs through crater and flank wear because of diffusion led by high cutting temperatures and subsequent chip adhesion to the tool flank face, accompanied by cutting edge chipping. Based on these results, a CBN cutting tool with a textured flank face was newly developed to improve the cutting tool life. Experimental: results showed that micro grooves generated on the flank face significantly suppressed the cutting edge chipping and remarkably extended the lifetime of the CBN tool during high-speed machining of Inconel 718.     

铸铁加工专用切削刀片的研制与应用

研制开发了用于铸铁切削的系列涂层刀片,介绍了该刀片的设计思路和研制方法,分析了刀片涂层的结构及特点。切削试验和用户试用结果表明,该系列刀片具有优异的切削性能。     

The lubricated wear of ceramics : Part II: The wear and friction of silicon nitride and steel in the presence of mineral oil or an ester based lubricant

The friction and wear characteristics of combinations of silicon nitride, alumina and AISI 52100 steel in the presence of mineral oil containing anti-wear, dispersant and detergent additives have been investigated in a tri-pin-on-disc machine. The tests were carried out at a nominal temperature of 100°C for a range of sliding speeds, loads and total sliding distances. In Part II of this two-part paper a comparison will be made between the tribological performance of these sliding pairs of materials in mineral oil and ester based lubricant environments. The results of the investigation showed that the alumina performed relatively poorly under these test conditions, whereas silicon nitride showed good potential as an improved wear resisting material compared with 52100 steel. Wear factors of the order of 10⁻¹⁰ mm³/Nm were deduced for the alumina, while values as low as 10⁻¹¹ mm³/Nm were typical of the silicon nitride sliding against 52100 steel discs. The alumina pins wore by a process of brittle fracture at the surface, whereas the silicon nitride pins wore primarily by a tribochemical polishing mechanism. The rate of tribo-chemical wear was found to be proportional to the nominal contact area.     

Tribological behaviour of plasma sprayed Al2O3 and TiO2 ceramic hard coatings under dry contact

Plasma sprayed ceramic coatings are used in a number of industries in which surface modification of components to compare tribological properties is important: so hence, are evaluations of their tribological properties. This paper presents a study on the wear behaviour of three ceramic coatings — Al₂O₃, TiO₂ and Al₂O₃-TiO₂combination — in the load and speed ranges of 5 to 50 N, and 0.3 to 10 m/s, respectively, on which few data are available in the literature. The tests were carried out using a standard dry sand rubber wheel abrasion test and a pin-on-disc machine under dry sliding conditions. It was found that a stick-slip effect seems to occur at low sliding speeds, and transition takes place at a sliding speed of around 4 m/s. Of the three ceramic coatings, TiO₂ was found to be the most wear resistant, with the least friction coefficient, although it is less hard than the Al₂O₃ coatings. Scanning electron microscopy of the surface shows evidence of wear mechanisms such as plastic deformation, transfer-film formation, micro cracks, and grain pull-out in the coatings.     

水蒸汽二次加热装置的研制及切削45钢的刀具磨损试验

研制了以过热水蒸汽作为冷却润滑剂的绿色切削技术所需供汽系统中的二次加热装置,并用该装置进行了不同切削速度下改变冷却润滑剂切削45钢时的刀具磨损对比试验。试验结果表明,该加热装置提供的过热水蒸汽状态稳定,且比干切削和以乳化液作冷却润滑剂时分别减小刀具磨损约50%和40%。     

混凝土与碾压混凝土断裂尺寸效应的研究进展

混凝土断裂力学是20世纪60年代基于金属断裂力学的基本理论基础,而发展起来的固体力学分支.它主要研究含裂缝体的混凝土材料和混凝土结构的破坏过程以及裂缝传播规律,建立断裂准则,探讨如何控制和防止混凝土结构断裂破坏的措施.本文综述了混凝土以及碾压混凝土断裂尺寸效应的现状进行了介绍和讨论.     

大口径油气管道坡口加工机床研制及其关键技术研究

建设中的中俄东线天然气管道工程在国内首次采用了φ1422 mm×80 mm钢管,最薄壁厚21.4 mm。详细介绍了φ1422 mm超大口径油气管道钢管坡口成型加工机床设计的技术方案,分析了保证坡口加工精度在设计过程中所采取的多项关键技术,提出了一体式定位、夹紧同步技术及浮动式切削技术,保证了坡口加工过程中的机床定位精度和切削精度。通过工程现场应用表明,该机床设计合理,运行性能平稳。     

Friction and wear behaviour of partially stabilised zirconia in reduced pressure atmospheres containing organic compounds: Potential for process lubrication of ceramics

Friction and wear tests were used to evaluate a partially stabilised zirconia (PSZ) disc rubbing against a PSZ pin in a high-vacuum sliding tester. The surrounding atmosphere contained an organic compound vapour (either benzene, acetone, methane or methanol) at a reduced pressure. In order to understand the mechanism of the tribochemical reaction, the sliding conditions, velocity, and load were varied. During the sliding test, the friction coefficient, surface electrostatic voltage, and adsorption behaviour were measured dynamically. After the sliding test, the worn surfaces were analysed with EPMA and TOF-SIMS to characterise the components and the molecular weight of the reaction products. The formation of sticky reaction products was observed on the sliding surface in benzene and acetone vapours. These products acted as lubricants, reducing the friction coefficients and wear rates. Analysis suggested that such sticky reaction products contained molecules up to 1000 atomic mass units (AMU).     

Development of novel sustainable neat-oil metal working fluids for stainless steel and titanium alloy machining. Part 1. Formulation development

This paper introduces and describes the development and application of methodologies for the formulation of novel sustainable neat-oil metal removal fluids. A further paper will describe the methodologies being employed and the results of the performance benchmarking of the final fluid formulations for stainless steel and aerospace-grade titanium alloy materials. In this paper, a stepwise approach to the development of novel sustainable neat-oil metal removal formulations is described with a detailed discussion and analysis of the approach taken and the methodologies developed and applied. Two target applications were identified for cutting stainless steel and aerospace-grade titanium alloys. The key required properties of the fluids for these applications were combined with targets identified for cost, low temperature properties, kinetic viscosity (KV) and oxidative stability. Samples of base oils were obtained and characterised. The oils ranged from commodity commercial and specialist natural vegetable oils to chemically modified vegetable-oil-derived fatty acid esters and polyols. The selected oils were used to create blends which were screened for their key properties. From this work, four blends of base oils were identified for being taken forwards to the formulation screening stage. These blends represented a range of natural and modified oils blended in such a way as to achieve all of the required key properties of cost, KV, melt/pour points and oxidative stability. To determine if the oils were likely to also perform well as metal cutting fluids, they were subjected to a range of tests with and without the addition of certain additives, and their performances were benchmarked against a range of mineral oil and polyol-ester-based commercial fluids currently supplied to the target applications areas. The tests employed were: SRV, microtap and oxidation stability. The issues involved in the extrapolation of results from tribological testing to the prediction of fluid cutting performance are highlighted and discussed. From this work, one base oil blend for each of the two target applications was identified and the best performing mineral and polyol ester benchmark fluids were selected. Full-scale drilling and rigid torque tapping tests were used to refine formulations and to screen other additives identified in parallel microtap tests. The durability, oxidation stability, machine tool compatibility and misting potentials of the final formulations were also benchmarked using a range of standard and novel methodologies—this work will be described in a later paper.