High Abrasive Wear Resistance Research Articles

Evaluation of magnetron-sputtered TiB 2 intended for tribological applications

To date, the coating industry has dramatically changed the possibilities for effective machining of many different materials. There are, however, some materials that still are problematic to machine. An example of such a material is particle-reinforced aluminium. For this material an effective tool material must possess high hardness to minimise abrasive wear. In addition, it must have a low adhesion to aluminium in order to prevent built-up edges. In respect of this TiB 2 is a very interesting material, because it exhibits a very high hardness and is inert to aluminium (liquid). The latter indicates a very low adhesion of aluminium on TiB 2. In this work, TiB 2 coatings were deposited by physical vapour deposition (PVD) on cemented carbide substrates using direct-current (DC) magnetron sputtering. The aim of the work was to evaluate how various deposition parameters, as well as the choice of working gas, influence the formation and tribological properties of TiB 2 coatings. All coatings were evaluated with respect to their phase composition, chemical composition, hardness, elasticity, residual stress, cohesion, adhesion and abrasive wear resistance. All the coatings displayed X-ray diffraction patterns of the hexagonal TiB 2 phase with a preferred (0001) orientation. Besides being very hard, all coatings were found to exhibit a high compressive residual stress level that was found to increase with negative substrate bias. The coating adhesion was found to be relatively good, whereas the coating cohesion was fairly low due to the high compressive stress in the coatings. Not surprisingly, all coatings displayed an extremely high abrasive wear resistance. It can be concluded that a PVD TiB 2 coating with good adhesion and overall good mechanical and tribological properties can be obtained, provided no negative substrate bias is used. A further improvement, in respect of lowering the residual stress, can be achieved by using xenon instead of argon as working gas.

Preparation of TiC films by alternate deposition of Ti and C layers using a dual magnetron sputtering source

Abstract Titanium carbide (TiC) films have been prepared by alternately depositing thin Ti and C layers on aluminosilicate glass substrate by magnetron sputtering. The apparatus used in the experiment was a dual-cathode-sputtering machine with a carousel type substrate holder. By rotating the substrate holder at a rotation speed of 30 rev/min, a thin Ti layer of 0–0.15 nm and a thin C layer of 0–0.072 nm depending on the cathode current were alternately deposited on the substrate. The Ti/C compositional ratios of films were controlled by varying the flux ratio (layer thickness ratio) of the Ti and C sources. This allowed films of Ti, TiC, and C to be prepared. The composition, structure, and hardness of the deposited films were estimated as a function of the source C/Ti flux ratio. The results of X-ray photoelectron spectroscopy showed that the film composition varied continuously from Ti:C=1:0 to 0:1, and that some oxygen was incorporated as an impurity for low C/Ti ratios. The X-ray diffraction measurement results showed that the film structure changed from α-Ti (obtained for a C/Ti flux ratio 0.5), and that the lattice spacing increased continuously with increasing C flux ratio for the polycrystalline TiC films. A maximum microhardness of about 17 GPa was obtained for films deposited at flux ratio of unity. In the sliding wear resistance test, higher abrasive wear resistance was observed for films deposited with C/Ti flux ratios of more than 0.33. The transition of the film structure and composition corresponds well to the film hardness and abrasive wear behavior.

Ultrahard Ti–B–N coatings obtained by reactive magnetron sputtering of a Ti–B target

The influence of the chemical composition of TiBN compounds on their properties was studied using cathodic reactive magnetron co-sputtering from a Ti and a TiB2 target. Five experiments have allowed to obtain 70 different composition points with N and B contents comprised between 0 and 60 at.%. Two domains with hardness over 50 GPa were identified. Only one domain shows very high abrasive wear resistance in water. The composition of this area is centred on compounds containing 20% B, 27% N and 53% Ti. A Ti–B target was then sintered to obtain this composition from a single target. By varying the nitrogen flow, one material with high abrasive wear resistance was elaborated. This material shows a f.c.c. structure with a lattice parameter of 0.432 nm. This coating contains 19% B, 26% N and 55% Ti. The microhardness was measured to be 44 GPa. Scratch testing indicates a cohesive failure mode with a critical load of 30 N. The abrasive wear resistance appears to be at least three times better than the wear resistance of TiN or CrN. The results obtained by co-sputtering and by sputtering of the Ti–B target show good correlation.

Performance of oxygen-rich TiALON coatings in dry cutting applications

Special research activities are concentrated on optimizing coating properties for improving the performance of tools in dry cutting applications. TiAlN-based hard coatings for dry cutting operations are well known for their high microhardness even at elevated temperatures as well as for their good oxidation resistance. A further improvement can be achieved by adding oxygen to deposit TiAlON. In dry drilling of tempered steel the wear mechanisms of oxygen-rich TiAlON-coated WC-carbide tools were investigated. Two possible approaches for plating TiAlON were examined: high ion sputtering (H.I.S.™) and the conventional magnetron sputter ion plating (MSIP). Graded and multilayer TiAlON coatings with varying oxygen contents were developed. Effects of the used deposition technology on coating structure, coating composition, strength and microhardness, as well as their influences on cutting performance were investigated. Highlighted are influences of oxygen-rich layers on wear behavior of TiAlN coatings in dry machining. Coating properties were characterized by SEM and EDX. Film adhesion was analyzed by scratch tests. In spite of reduced microhardness of TiAlON coatings high abrasive wear resistance in dry drilling of tempered steel could be reached due to improved high-temperature properties of TiAlON films.

High Cycle Fatigue and Abrasive Wear Resistance Properties of PDI, Gas-Carburizing-Treated PDI and ADI.

With a gas carburizing treatment processed to pearlitic ductile cast iron (CPDI), the investigations were carried out about its high cycle fatigue strength and abrasive wear resistance. The high cycle fatigue strength were evaluated by rotating bending fatigue tests, and the fatigue strength was improved about 20 MPa greater than virgin test pieces not-carburized (PDI). The crack initiating point and fracture is from irregular graphites of surface or from microdefects in casting, which PDI and CPDI specimens were not in an inner type fracture. Furthermore, a good result was obtained in the abrasive wear resistance test than in that of austempered ductile cast iron (ADI). Those were expressed by the difference of matrix structures. Its matrix structure of CPDI is transformed a martensite structure from SEM observation.

Carbon-based coatings for dry sheet-metal working

This paper describes recent advances in the coating of tools for forming processes such as deep drawing or clinching of aluminium and stainless-steel sheets. Various carbon-based coatings, prepared by PECVD (RF and pulsed-DC mode) and by reactive DC magnetron sputtering have been investigated with respect to hardness, abrasive wear resistance, adhesion properties and tribological behaviour under forming conditions. The softer and less wear-resistant coatings exhibited the lowest adhesive wear and friction against aluminium and stainless-steel counterparts. Application tests with coated tools were carried out under near production conditions. Correlation of mechanical test results with the film behaviour under service shows that for the dry forming of stainless steel, a high abrasive wear resistance of the hydrocarbon coating is necessary. No cold welding of the steel sheets on the tools was found, so the aim of dry working is reached by these coatings. For forming of aluminium, only softer a-C:H coatings showed satisfying anti-galling properties. In particular, in the case of aluminium working with a high degree of form change, there is a need for coatings with further improved anti-galling properties.

Tribological evaluation of thermally activated CVD diamond-like carbon (DLC) coatings

Diamond-like carbon coatings have been the subject of expanding technological interest for wear resistance and low friction applications during recent years. In this study, diamond-like carbon coatings were deposited by thermally activated chemical vapour deposition. The deposition temperature was 900°C and CH 2I 2 was used as a precursor. Tribological evaluation was performed by surface roughness measurement together with hardness, micro abrasion and friction. Furthermore, the residual stress of the coating was evaluated by a deflection method. The coating was analysed with nuclear reaction analysis, scanning electron microscopy and atomic force microscopy. The coating was very smooth ( R a = 1 nm) and free from pores. A high abrasive wear resistance slightly worse than physical-vapour-deposited TiN was measured. It exhibit a hardness of 2800 HV and a friction coefficient of about 0.2 in air (30–50% relative humididty). Furthermore, the coating has a compressive residual stress of 220 MPa. Hydrogen content and density of the coating were 9 at.% and 1.8 g cm −3, respectively.

Study of metal containing hydrogenated carbon films by STM/AFM and SAXS

Metal-containing amorphous hydrogenated carbon films are of high interest for industrial applications because of their excellent frictional properties, their high abrasive wear resistance and their electrical conductivity, which can be adjusted in a range of 10–12 orders of magnitude. In order to get insight into the mechanical and electrical properties it is necessary to study the nanostructure of the films. The structure consists of small nanometer sized metallic or carbidic particles, which are embedded in a three dimensional amorphous hydrogen-carbon matrix. Anomalous small angle X-ray scattering (ASAXS) and scanning tunneling microscopy (STM) have been used to determine size- and distance-distributions of the particles as a function of metal content. Problems and restrictions of both methods will be discussed. Furthermore the capabilities of scanning probe techniques to distinguish different materials on a nanometer scale (material contrast) have been studied employing barrier height imaging (dI/dz) and friction force microscopy.

Abrasive wear of aluminium composites—a review

Aluminium-silicon alloys and aluminium-based metal-matrix composites (MMCs) containing hard particles offer superior operating performance and resistance to wear. In industrial processes where abrasive slurries are transported by rotating paddles or impellers, clements fabricated from MMC materials provide higher abrasive resistance and therefore a longer service life compared to those made from iron or nickel-based alloys. Composites characterized by a hardness greater than the abrasive particles and a reinforcement phase of high fracture toughness and low mean free path, compared to the abrasive grift dimension, exhibit high abrasive wear resistance. Studies related to abrasive wear of AlSi alloys and aluminium-based MMCs that contain discontinuous reinforcement phases are reviewed.

Effect of alloying on the wear resistance of cast steel

We study the influence of rare-earth metals on physicomechanical properties and wear resistance of cast tool steel and establish the optimal content of carbon (0.55–0.65%) which guarantees sufficiently high abrasive wear resistance of steel. Alloying with titanium, niobium, and rare-earth metals improves wear resistance of steels, especially with elevated contents of carbon.

Features of structural transformations for cast iron IChKh12M with rapid heating for hardening

1. With accelerated heating up to the melting temperature during heat treatment for cast iron IChKh12M a composite structure is retained: a skeleton of primary ledeburite carbides included in a matrix of variable structure. 2. Use of accelerated austenitizing causes formation of a nonuniform solid solution of austenite in the cast iron matrix. Variation of the heating temperature and cooling rate makes it possible to change within wide limits the structure of the matrix and cast iron properties. An increase in heating temperature followed by slow cooling changes the cast iron matrix structure from pearlite-bainite to bainite-martensite. After quenching there is formation of a martensite-austenite structure. 3. Accelerated heating shifts the temperature of phase transitions for cast iron into a higher temperature region compared with furnace heating. On the basis of this an optimum heat treatment schedule was developed for cast iron IChKh12M which makes it possible to obtain high abrasive wear resistance. Heat treatment with heating for hardening in molten salts or electric heating is recommended for articles of cast iron IChKh12M which operate under abrasive wear conditions.

Comparative Wear Tests of Different Types of Coatings on Steels

AbstractDifferent coatings were formed by galvanical deposition, thermochemical treatment, CVD, PVD or plasma spraying. Their wear behaviour was tested under various conditions so that adhesive and abrasive wear mechanisms predominated. The resistance of the coatings to adhesive failure and wear was examined with the pin and disc system under conditions of boundary lubrication. The discs were protected by different coatings while the pins were made of tool steel or alumina. For abrasive wear tests a grinding apparatus with grinding papers of flint, alumina or silicon carbide was used. From the resultsthe following conclusions can be drawn: -Thermochemically treated steels and nickel-phosphorus coatings have a high resistance to galling if the counterbody consists of steel or alumina. The couples plasma sprayed molybdenum against steel and tungsten carbide against alumina also have a high resistance against galling.-The wear of most coatings is low if the counterbody is made of steel. By analumina counterbody the wear of the coatings isincreased. Alumina is worn less by the coatings than steel.-The hard CVD- and PVD-coatings, the thermochemically formed iron boride andvanadium carbide coatings and the electroless nickel-phosphorus-diamond coatings have a high abrasive wear resistance.

Increasing the abrasive wear resistance of steel 120G13

1. To obtain an alloy with high abrasive wear resistance, it must have a eutectic structure in which the hard phase separates out in the form of thin ramified crystals acting as microreinforcement of the metallic matrix. 2. A eutectic alloy whose metallic matrix has the composition of steel 120G13 and whose strengthening phase is titanium diboride has in the cast state an abrasive wear resistance that is several times greater then the abrasive wear resistance of steel 120G13.

Influence of hardness and structure of the pins on the wear resistance of track hinges

1. The optimum structure of the hardened layer of track pins of medium carbon steels providing high abrasive wear resistance of the track hinge is uniform untempered or low-temperature tempered martensite with a hardness of≥Rockwell C 60, which is obtained by surface induction hardening from 980–1020°C with spray cooling by water. 2. A decrease in surface hardness of the pins to Rockwell C 54 (lower limit according to specifications) as a result of tempering or of the appearance in the structure of the hardened layer of areas of troostite does not have a marked influence on the wear resistance of the pins themselves but does cause a sharp (by ∼1.7 times) decrease in the wear resistance of the link lugs in contact with them. 3. The martensitic grain size (the austentic grain size) of the hardened layer of pins of medium carbon steels does not have a substantial influence on the abrasive wear resistance of both the pins themselves and on the link lugs in contact with them. 4. Alloying of medium carbon steel with chromium, manganese, silicon, and microadditions of vanadium and also combined alloying with these elements with hardening of pins to the same structure and hardness does not influence the abrasive wear resistance of a track hinge but may provide an additional increase in the wear resistance of the contacting link lugs as a result of obtaining a stable optimum martensitic structure in the pins within the limits of the whole 3.5-mm-thick layer which wears in service.

Influence of electric spark alloying parameters on the hardness and wear resistance of the metallic surface

1. For the electrode materials investigated, the optimum power of electrical discharge is between 2 and 3 J, the optimum specific process duration being 1 sec/mm2. 2. The highest abrasive wear resistance is exhibited by surfaces alloyed with titanium and zirconium diborides, as well as with chromium, titanium, and boron carbides. 3. The alloying of the steel surface with titanium carbide in a nitrogen atmosphere raises the surface microhardness by 20–25% above that secured by alloying in air.