Nanoscratch and nanowear testing of TiN coatings on M42 steel

Abstract

Constant load, progressive load and multipass nanoscratch (nanowear) tests were carried out on 500 and 1500 nm TiN coatings on M42 steel chosen as model systems. The influences of film thickness, coating roughness, scratch direction relative to the grinding grooves on the critical load in the progressive load test and number of cycles to failure in the wear test have been determined. Progress towards the development of a suitable methodology for determining the scratch hardness from nanoscratch tests is discussed.     

Atomistic Insights on the Wear/Friction Behavior of Nanocrystalline Ferrite During Nanoscratching as Revealed by Molecular Dynamics

Using embedded atom method potential, extensive large-scale molecular dynamics (MD) simulations of nanoindentation/nanoscratching of nanocrystalline (nc) iron have been carried out to explore grain size dependence of wear response. MD results show no clear dependence of the frictional and normal forces on the grain size, and the single-crystal (sc) iron has higher frictional and normal force compared to nc-samples. For all samples, the dislocation-mediated mechanism is the primary cause of plastic deformation in both nanoindentation/nanoscratch. However, secondary cooperative mechanisms are varied significantly according to grain size. Pileup formation was observed in the front of and sideways of the tool, and they exhibit strong dependence on grain orientation rather than grain size. Tip size has significant impact on nanoscratch characteristics; both frictional and normal forces monotonically increase as tip radii increase, while the friction coefficient value drops by about 38%. Additionally, the increase in scratch depth leads to an increase in frictional and normal forces as well as friction coefficient. To elucidate the relevance of indentation/scratch results with mechanical properties, uniaxial tensile test was performed for nc-samples, and the result indicates the existence of both the regular and inverse Hall–Petch relations at critical grain size of 110.9 Å. The present results suggest that indentation/scratch hardness has no apparent correlation with the mechanical properties of the substrate, whereas the plastic deformation has.     

Effects of normal load on single-pass scratching of polymer surfaces

The effects of normal load and the resulting scratch depth on scratch force profile, scratch hardness and the mechanisms of deformation and material removal for a number of industrially important polymers are studied. Upon scratching by a 30° angled conical tip, the mean tangential or scratch force is found to be linearly related to the normal load at lower speed (0.2 mm s⁻¹); however, at higher scratching speed (2.0 mm s⁻¹), there is a decrease in the slope of the scratch force versus normal load curve for all polymers. The phenomenon of stick-slip is severe at higher normal loads and scratch depths for the polymers that show ductile nature. The scratch hardness for softer polymers tends to decrease with normal load, whereas for harder polymers, scratch hardness increases for intermediate loads and tends to decrease at very high loads. The deformation mechanism, to a large extent, is insensitive to the imposed normal load or the depth of scratching; however, material removal and debris formation process depends upon the scratch depth.     

On the effect of crystallographic orientation on ductile material removal in silicon

In this work the critical chip thickness for ductile regime machining of monocrystalline, electronic-grade silicon is measured as a function of crystallographic orientation on the (0 0 1) cubic face. A single-point diamond flycutting setup allows sub-micrometer, non-overlapping cuts in any direction while minimizing tool track length and sensitivity to workpiece flatness. Cutting tests are performed using chemically faceted, −45° rake angle diamond tools at cutting speeds of 1400 and 5600 mm/s. Inspection of the machined silicon workpiece using optical microscopy allows calculation of the critical chip thickness as a function of crystallographic orientation for different cutting conditions and workpiece orientations. Results show that the critical chip thickness in silicon for ductile material removal reaches a maximum of 120 nm in the [1 0 0] direction and a minimum of 40 nm in the [1 1 0] direction. These results agree with the more qualitative results of many previous efforts.     

The scanning micro-sclerometer: a new method for scratch hardness mapping

A new surface engineering research tool, called a scanning microsclerometer (SMS), has been developed. It uses nano-indentation technology and a piezoelectric transducer positioning system to generate high-precision scratch patterns on the surfaces of metals and, by monitoring the instantaneous displacement of the stylus tip, can generate scratch hardness and scratching force maps of the surface. A dual-stroke process is used. The first stroke at low load profiles the surface to establish a reference datum and the second pass, in the opposite direction and at higher load, produces the indentation scratch. Examples of micro-scratch hardness mapping experiments, using scratch spacings of 1·0 μm, on a silicon carbide-based ceramic composite are used to illustrate the capabilities of the SIVIS. Using end-on fibers in the rectangular stylus scanning area, the difference in scratch hardnesses of the fibers, the matrix, and even the thin carbon coatings in the fiber-matrix interface could be detected. The SMS was originally developed to produce scratch hardness maps, but it is also useful for conducting accurately controlled, single-point micro-machining patterns and in studies of differential material abrasion.     

Effects of probe tilt on nanoscratch results: An investigation by finite element analysis

The purpose of this paper is to investigate the effects of probe tilt on the results of nanoscratch by finite element analysis (FEA). In nanoscratch experiments, it is hard to assure absolute verticality between the scratch probe and the specimen. Simulation results show that different tilt cases of the probe have different extents of influences on the residual scratch profile, the projected contact area and the frictional coefficient of nanoscratch results. To get reliable results from the nanoscratch experiments, the verticality between the scratch probe and the specimen should be accurately guaranteed. On the other hand, the tilt phenomenon of the probe can also be used to obtain some wanted profiles.     

Low Temperature Nano-Tribological Study on a Functionally Graded Tribological Coating Using Nanoscratch Tests

Previous studies on low temperature tribological investigations were limited to macro-scale studies because of the lack of suitable instrumentation. This limitation has been overcome using a newly developed low temperature nanoscratch tester capable of characterizing the scratch resistance of coatings down to −30 °C. The scratch resistance and mechanical properties of a functionally graded a-C:H(Ti)/TiCN/TiN/Ti coating have been investigated for temperatures ranging from 25 to −30 °C. It has been found that the a-C:H(Ti)/TiCN/TiN/Ti coating failed at high loads by cracking and spallation during the room-temperature scratch tests. Fractography suggests that these failures originate from or close to the interface between the top a-C:H(Ti) and the TiCN layers. Decreasing the test temperature from 25 to 0 °C resulted in increased values in H, H/E _r and H ³ /E _r², consistent with improved crack- and wear resistances, with further smaller improvements being achieved on further decreasing the temperature to −30 °C.     

单晶蓝宝石的延性研磨加工

为实现单晶蓝宝石的延性研磨加工,采用纳米压痕和划痕法测试并分析了单晶蓝宝石(0001)面的微纳力学特性,建立了单颗圆锥状磨粒的压入模型并计算了延性研磨加工的受力临界条件,分析了金刚石磨粒嵌入合成锡研磨盘表面的效果.对单晶蓝宝石进行了延性研磨加工试验,采用NT9800白光干涉仪、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等方法分析了单晶蓝宝石的延性研磨表面特征.试验结果表明:采用纳米压痕和划痕法可以为单晶蓝宝石的延性研磨加工提供工艺参数,单晶蓝宝石的延性堆积的极限深度为100 nm,金刚石磨粒的嵌入及在适当载荷下可以实现蓝宝石的延性研磨加工,实验条件下的最佳载荷为21 kPa,延性研磨后单晶蓝宝石表面划痕深度的分布情况较好,分散性小,研磨后的表面发生了位错滑移变形.     

Nanotribological and nanomechanical characterization of human hair using a nanoscratch technique

Human hair ( approximately 50-100 microm in diameter) is a nanocomposite biological fiber with well-characterized microstructures, and is of great interest for both cosmetic science and materials science. Characterization of nanotribological and nanomechanical properties of human hair including the coefficient of friction and scratch resistance is essential to develop better shampoo and conditioner products and advance biological and cosmetic science. In this paper, the coefficient of friction and scratch resistance of Caucasian and Asian hair at virgin, chemo-mechanically damaged, and conditioner-treated conditions are measured using a nanoscratch technique with a Nano Indenter II system. The scratch tests were performed on both the single cuticle cell and multiple cuticle cells of each hair sample, and the scratch wear tracks were studied using scanning electron microscopy (SEM) after the scratch tests. The effect of soaking on the coefficient of friction, scratch resistance, hardness and Young's modulus of hair surface were also studied by performing experiments on hair samples which had been soaked in de-ionized water for 5 min. The nanotribological and nanomechanical properties of human hair as a function of hair structure (hair of different ethnicity), damage, treatment and soaking are discussed.     

Mechanical and Tribological Properties of Diamond-Like Carbon Films Deposited by Electron Cyclotron Resonance Microwave Plasma Chemical Vapor Deposition

Mechanical and tribological properties of diamond-like carbon (DLC) films deposited by electron cyclotron resonance microwave plasma chemical vapor deposition were analyzed by nanoindentation, nanoscratch and ball-on-disk sliding tests. As the results, hardness and residual stress which depended on the substrate bias voltage had combined effects on the scratch resistance of the films. In sliding friction tests, the transferred layer on the surface of the counterpart accounts for the decrease of friction coefficient with increasing sliding distance. Atomic force microscopic images of the DLC films and the counterpart Si₃N₄ ball surfaces indicate that the sliding friction process could be treated as a periodical scratching process with many indenters.     

Use of nanoindentaion and nanoscratch experiments to reveal the mechanical behavior of POSS containing polyurethane nanocomposite coatings: The role of functionality

Organic–inorganic polyurethane coatings were prepared using two polyester resins and two polyhedral Oligomeric Silsesquixane (POSS) compounds. The effect of hydroxyl content and POSS functionality was studied on hardness and scratch resistance. FTIR spectroscopy was used to reveal bond formation between isocyanate and hydroxyl groups. Vickers hardness, nanoindentaion and nanoscratch experiments were performed to study the mechanical properties of the hybrids. The results showed that intrinsic hardness of POSS affected the crosslink density, the result of which was increased free volume and improved scratch resistance of POSS/PU hybrid coatings. This behavior was dependent on the hydroxyl percent of the polyol.     

Experimental study of crystal anisotropy based on ultra-precision cylindrical turning of single-crystal calcium fluoride

To realize ultimately efficient signal processing, it is necessary to replace electrical signal processing circuits with optical ones. The optical micro-resonator, which localizes light at a certain spot, is an essential component in optical signal processing. Single-crystal calcium fluoride (CaF₂) is the most suitable material for a highly efficient optical micro-resonator. The CaF₂ resonator can only be manufactured by ultra-precision machining processes, because its crystal anisotropy does not allow the application of chemical etching. However, the optical micro-resonator's performance depends definitely on the surface integrity.This study investigated the relationship between surface quality after ultra-precision machining and crystal anisotropy. Firstly, crack initiation was investigated on the (1 0 0), (1 1 0), and (1 1 1) planes using the micro-Vickers hardness test. Secondly, brittle-ductile transition was investigated by orthogonal cutting tests. Finally, cutting performance of cylindrical turning was evaluated, which could be a suitable method for manufacturing the CaF₂ resonator. The most difficult point in cylindrical turning of CaF₂ is that the crystalline plane and cutting direction vary continuously. In order to manufacture the CaF₂ optical micro-resonator more efficiently, analysis was conducted on crack initiation and surface quality of all crystallographic orientations from the perspective of slip system and cleavage.     

Anisotropic Wear Resistance of Human Mandible Cortical Bone

In order to evaluate the wear resistance, nanoscratch tests were conducted along different directions in the axial and the cross sections of mandible cortical bone, with the progressive loads from 0.1 to 80 mN. The morphology of scratch scars was showed via a field emission scanning electron microscope and an AMBIOS XP-2 stylus profilometer. The results indicated that the wear resistance of axial section was better than that of cross section. Furthermore, the wear resistance of axial section was affected by the different arrangement of lamellae. The wear degree was slighter when the scratches were conducted along the direction paralleling the osteon. The wear mechanism of cortical bone became more complicated with the increasing loads. It changed from the simple elastic–plastic deformation to the combination of deformation, delamination, and microcrack’s propagation.     

Electrostatic force microscopy study on the domain switching properties of the Pb(Zr0.2Ti0.8)O3 thin films with different crystallographic orientations for the probe-based data storage

The domain switching properties of the ferroelectric Pb(Zr_0.2Ti_0.8)O₃ (PZT) thin films with two types of crystallographic orientations were investigated by electrostatic force microscopy (EFM). The crystallographic orientations of the PZT thin films were random on the (1 1 1)Pt/MgO(1 0 0) and c-axis preferred on the (1 0 0)Pt/MgO(1 0 0), respectively. When dc bias was applied to the films for writing in micro-scale area, electrostatic force images showed that the domain switching was hard in the PZT thin films with random orientation, while the pattern could clearly be written in the PZT films with c-axis orientation. The differences in the domain switching properties of each PZT thin film were investigated in the crystallographic orientations point of view, and the domain switching dynamics were also measured by investigating the nano-sized dot switching behavior with respect to the width of the applied voltage pulse.     

Fretting on the cubic face of a single-crystal Ni-base superalloy at room temperature

Fretting experiments were conducted on the (1 0 0) crystal (cubic) face of a single crystal Ni-base superalloy in two directions, 〈1 0 0〉 and 〈1 1 0〉, to study the effect of crystallographic orientation on the fretting response in both partial slip and gross slip regimes. The study involved point contacts using a tungsten carbide (WC) ball with radius 10 mm tested at room temperature. Ball indentation was used to determine secondary crystallographic orientations. Under sufficiently high normal force, the friction on the cubic face in the 〈1 1 0〉 direction was larger than in the 〈1 0 0〉 direction. This difference can be explained by the extent of plastic deformation in the surface layer and associated microstructure changes, both of which depend on the coupling between the crystallographic orientation and the cyclic deformation field.     

Nanomechanical characterization of skin and skin cream

The mechanical properties of skin are an important characteristic of its resistance to damage and important indicators of pathological situations. Skin care products are the most common method to improve skin health and create a smooth, soft, and elastic perception by altering the mechanical properties of skin. It is of interest to study how skin cream affects the mechanical properties of skin. It also can help to quantify the effectiveness of cosmetic products. In this study, we present a systematic study of the mechanical properties of virgin skin and cream-treated skin. In nanoscratch measurements, the scratch wear tracks were generated at various loads using an atomic force microscope. Hardness and elastic moduli were measured using a nanoindenter. The in situ tensile properties of virgin skin and cream-treated skin were measured using a custom-built tensile stage that attaches to the atomic force microscope. Compared with virgin skin, cream-treated skin exhibits better scratch resistance up to a normal load of 15 μN. The indentation hardness and elastic modulus of cream-treated skin are lower than that of virgin skin, indicating that the skin cream moistens and softens the skin surface. In the stretching experiments, the elastic modulus is lower and ultimate strain is higher than that of virgin skin, indicating skin cream can improve the tensile response of skin. Mechanisms for the observed trends are discussed.     

锗单晶的各向异性对单点金刚石切削的影响

锗单晶是一种各向异性材料,在切削的过程中,将使切削力随晶向和晶面发生变化。针对锗单晶各向异性对切削力的影响,在理论上计算出了切削力随不同晶面和晶向变化的波动范围,并且指出了最佳的切削方向。     

易解理氧化镓晶体微尺度力学行为试验研究

为了探寻单晶氧化镓晶体超精密加工的易切削方向以及临界切削深度,将单晶氧化镓晶体(100)晶面和(010)晶面等角度划分成24等份,对每个方向上用Berkovich金刚石压头进行纳米压痕试验、用Cube金刚石压头进行纳米压痕和划痕试验。试验结果表明,在(100)晶面120°方向上脆塑转变临界切深最大,为623 nm左右,此时脆塑转变临界载荷为29.4 mN;在(010)晶面105°方向上脆塑转变临界切深最大,为686 nm左右,此时脆塑转变临界载荷为20.0 mN。氧化镓晶体存在强烈的各向异性,其中(010)面各向异性较为强烈。对比硬度、弹性模量、断裂韧度和相对脆塑转变临界切深随方向的变化趋势,结合各方向的划痕试验结果可以看出,氧化镓晶体(010)面为易加工晶面,105°方向为易加工方向。     

The scratch hardness and friction of a soft rigid-plastic solid

The paper describes an experimental and analytical study of the normal and scratch hardnesses of a model soft rigid-plastic solid. The material known as ‘Plasticine’, a mixture of dry particles and a mineral oil, has been deformed with a range of rigid conical indentors with included angles of between 30° and 170°. The sliding velocity dependence of the computed scratch hardness and friction has been examined in the velocity range 0.19 mm/s to 7.3 m/s. Data are also described for the time dependence of the normal hardness and also the estimated rate dependence of the intrinsic flow stress. The latter values were estimated from data obtained during the upsetting of right cylinders. Three major conclusions are drawn from these data and the associated analysis. (1) A first-order account of the scratching force may be provided by adopting a model which sums the computed plastic deformation and interfacial sliding contributions to the total sliding work. This is tantamount to the adoption of the two-term non-interacting model of friction. (2) For this system during sliding, at high sliding velocities at least, the interface shear stress which defines the boundary condition is not directly related to the bulk shear stress. The interface rheological characteristics indicate an appreciable dependence on the imposed strain or strain rate. In particular, the relative contributions of the slip and stick boundary conditions appear to be a function of the imposed sliding velocity. (3) The computed normal and scratch hardness values are not simply interrelated primarily because of the evolving boundary conditions which appear to exist in the scratching experiments.