Surface structure of stainless and Hadfield steel after impact wear

After impact wear, the very surface of stainless austenitic CrMnCN steel and austenitic MnC Hadfield steel revealed a thin fully amorphous layer followed by a layer of nanocrystals embedded in an amorphous surrounding, which was supported by a severely cold worked layer of austenite below. The new high-strength stainless steel contained C + N = 0.82 mass% and exceeded Hadfield steel in respect to proof strength, elongation, work to fracture and wear rate.     

Effect of surface nanocrystallization on abrasive wear properties in Hadfield steel

A nanocrystalline surface layer was synthesized on a Hadfield steel by shot peening treatment. The microstructure evolvement of the surface layer of the shot peening treated sample was characterized by optical microscopy, X-ray diffraction and high-resolution transmission electron microscopy. It has been shown that the grain sizes in surface layer were decreased to 11.1-17.4 nm after 60 min shot peening duration. Surface hardness was also increased greatly. Two- and three-body abrasive wear experiments were carried out for work hardening and original specimens, separately. The results showed that the wear resistance of the nanocrystallized Hadfield steel has distinctly been improved in case of soft particles used as two-body wear abrasives or light impact load applied for impact abrasive wear.     

Impact of plasma hardening on the wear resistance of 38XC steel

The impact of plasma hardening on the wear resistance of 38XC steel was studied. It has been found that the wear resistance increases by 53.7 times under the condition of dry friction compared to the normalized state and by 12.7 times compared to the improved state. During plasma hardening, the wear of 38XC steel under dry friction is equal to the normalized steel 15 with lubrication; and the wear is not increased in case of a 1.5-fold increase in the load. The addition of HADO revitalizant to oil contributed to an approximately twofold decrease in the wear of 38XC steel with plasma hardening during wearing-in after cutting off the lubricant.     

Impact wear of a tool steel

Results from wear studies in repetitive impact sliding are described in this paper. The material pair studied consisted of steel CPM-10V (specimen) (where CPM denotes crucible particle metallurgy) and 17-4 precipitationhardened (PH) steel (counterface) with transverse sliding velocities of 4 and 8 m s^?1. By means of scanning electron microscopy, energy-dispersive analysis of X-rays and X-ray diffraction methods it is shown that the wear is due to a material transport of the counterface 17-4 PH steel to the CPM-10V surface. In the wear process, a change in microhardness of the counterface substrate is apparent, and X-ray diffraction of debris confirms the presence of transformed metal. These products include γ-Fe together with trace amounts of α-Fe₂O₃; however, virtually no carbide from the CPM-10V steel was detected.     

Investigation of abrasive wear resistance and wear mechanism of composite alloys

The abrasive wear resistance of composite alloys comprising hard tungsten carbide and soft CuNiMn matrix under different wear conditions has been investigated and compared with CrMo cast iron. It was found that Yz-composite alloy with hard cast angular tungsten carbide has greater wear resistance than CrMo cast iron under two-body wear conditions, but lower resistance than Cr-Mo cast iron under three-body wear conditions. It was found that under three-body wear conditions selective wear of the matrix and digging or fragmentation of tungsten carbide particles dominate in Yz-composite alloy, and microcutting and deformed ploughing is dominant under two-body wear conditions. The abrasive wear resistance of composite alloys under two-body wear condition is independent of bulk hardness, but is closely related to the microhardness of tungsten carbide.     

Impact wear model for steel specimens

A rational model for estimating zero wear conditions in the compound impact (impact accompanied by sliding) wear mode is proposed. One-body wear and the moderate (elastic) stress range is considered. It is argued that a zero wear limit condition occurs as a result of fatigue of the material near and below the surface. On this basis in-depth and surface contributions to “damage” are calculated, and a “wear factor” is derived. The experimental work well supports the basic tenets of the model; i.e. the existence of a discrete wear factor and the dependence of wear on two crucial parameters: the sliding speed and the stress ratio.     

Abrasive wear resistance of textured steel rings

The fundamental aim of the present research is to study the effect of dimple shape and area density on abrasive wear in lubricated sliding. The other aims are to recommend a method of obtaining the local linear wear of a textured ring on the basis of profilometric measurement and to analyse the changes in the surface topography of this ring with selection of parameters that could monitor the “zero-wear” process.The experiments were conducted on a block-on ring tester. The stationary block made from cast iron of 50 HRC hardness was ground. The rotated ground ring was made from 42CrMO4 steel of 32 HRC hardness. The rings were modified by a burnishing technique in order to obtain surfaces with oil pockets. Oil pockets of spherical and of drop shape were tested. The pit-area ratios were in the range: 7.5–20%. The tested assembly was lubricated by oil L-AN 46. Because of the great hardness of the co-acting parts the wear resistance test was carried out under artificially increased dustiness conditions. The dust consists mainly of SiO₂ and Al₂O₃ particles. Measurement of local microscopic ring wear was made using a three-dimensional scanning instrument. The tendencies of ring surface topography changes during wear were analysed. Various methods of obtaining the local wear value during a low wear process were proposed and compared. We found that a spherical shape of dimples was superior to a drop shape with regard to wear resistance of steel rings.     

Laser composite surfacing of AISI 304 stainless steel with titanium boride for improved wear resistance

The present study concerns development of a hard in situ boride-dispersed composite layer on the surface of AISI 304 stainless steel substrate to improve the wear resistance property. Laser processing was carried out by melting the surface of sand-blasted AISI 304 stainless steel substrate using a continuous wave CO₂ laser and simultaneous deposition of a mixture of K₂TiF₆ (potassium titanium hexafluoride) and KBF₆ (potassium hexafloroborate) (in the weight ratio of 2:1) using Ar as shrouding environment. Powder feed rate was maintained constant at 4 g/min. Irradiation results in dissociation of a pre-deposited mixture along with a part of the stainless steel substrate, intermixing and rapid solidification to form the composite layer on the surface. The micro-structure of composite layer consists of dispersion of titanium boride particles in AISI 304 stainless steel matrix. Volume fraction of particles is found to be uniform throughout the composite layer, though varied with laser parameters. The micro-hardness of the surface was improved 250–350 VHN as compared to 220 VHN of the AISI 304 stainless steel substrate with a significant improvement in wear resistance property. The mechanism of wear was found to be a combination of adhesive and abrasive in as-received stainless steel. However, it was predominantly abrasive for laser composite surfaced stainless steel.     

Abrasive wear characteristics of a zinc-based alloy and zinc-alloy/SiC composite

An attempt has been made in this investigation to assess the contribution of various parameters towards governing the abrasive wear response of a zinc-based alloy under the conditions of varying applied loads and sliding distances. The factors whose contribution has been examined include deterioration in the cutting efficiency of the abrasive medium, role played by the SiC particles (dispersed in the alloy matrix) in terms of their degradation and resistance offered by them against the destructive action of the abrasive, subsurface hardening of the matrix and such other related aspects. Four types of abrasion tests were conducted on the samples to achieve the goal. The (abrasion) tests involved the use of (i) fresh as well as preworn surfaces of the samples and (ii) fresh and degraded abrasive media in four different combinations.The study suggests that the mentioned factors contribute to a varying degree towards controlling the (high-stress) abrasive wear behaviour of the specimens. However, degradation in the cutting efficiency of the abrasive medium (through capping, clogging, attrition and shelling) dominates over the influence of other parameters such as abrasion induced subsurface hardening of the matrix. Reinforcement of the SiC particles in the alloy matrix offered improved wear resistance (inverse of wear rate) under less severe conditions such as at low applied loads, wherein the dispersoid (SiC) particles could be retained by the matrix due to low cutting depths made by the abrasive particles. The dispersoid particles deteriorated the wear response of the matrix under more severe conditions of abrasion, such as at high loads, because of larger cutting depths causing fracturing and partial removal of the reinforcement (SiC) particles. The observed wear response of the samples has further been substantiated through the characteristics of wear surfaces, debris particles and abrasive medium after testing the matrix alloy and composite in a typical test condition expected to affect the abrasive medium and test specimens to the largest extent.     

Sliding wear characteristics of gas boronized steel

The wear characteristics and the mechanism of sliding wear of boronized steel under unlubricated conditions were studied. Characteristic wear curves of FeB and Fe₂B boride layers formed on SAE 1045 steel were similar in form. The maximum wear rates were obtained under a sliding velocity of 0.30 m s^?1 for FeB specimens and 0.50 m s^?1 for Fe₂B specimens. Under such conditions both mechanical wear caused by scratching and oxidative wear occurred. Under conditions of mild wear the wear loss was caused mainly by oxidative wear. Under conditions of heavy wear destruction of the sliding surface was caused by thermal stress. The wear debris was composed principally of iron oxides (α Fe₂O₃, Fe₃O₄) formed by oxidative wear, α iron and borides (FeB, Fe₂B) produced by mechanical wear and B₂O₃ produced by the preferential oxidation of boron in the boride layer.     

Dry friction and wear characteristics of nickel/carbon nanotube electroless composite deposits

Ni/carbon nanotube (Ni/CNTs) composite coatings were deposited on carbon steel plate by electroless deposition. The friction and wear properties were examined under dry sliding conditions using the ball-on-disk configuration. For reference, carbon steel plate was coated with Ni, Ni/SiC and Ni/graphite. The results show that the Ni/CNT coating has a microhardness value of 865 Hv, greater than for SiC reinforced composite deposits. The Ni/CNTs composite coating possesses not only a higher wear resistance but also a lower friction coefficient, resulting from their improved mechanical characteristics and the unique topological structure of the hollow nanotubes.     

The dry wear resistance of a carbonitrided steel

Rolling-sliding tests on a low alloy carbonitrided steel were carried out in order to study its dry wear behaviour. The influence of different retained austenite contents was evaluated. Subsurface fatigue is considered to be the basic wear mechanism. The similar wear resistances shown in specimens with small and large amounts of retained austenite are attributed to the balancing effect on their mechanical properties of softening by dynamical recovery and hardening by plastic strain respectively.     

Unlubricated wear of Si/SiC and its composite with nickel Si/SiC-Ni

Using a pin-on-disk tribometer, dry friction and wear properties at different temperatures were investigated for reaction-sintered silicon carbide Si/SiC and its composites with nickel Si/SiC-Ni. The friction and wear properties of the composites are improved by the addition of nickel. The analysis on the worn surfaces and sub-surfaces by SEM suggest that shallow grooves are the main wear feature at 15°C. At 600°C, surface cracking and fracture is the predominating wear mechanism for Si/SiC, and the formation of flake pits on the surface due to crack propagation at subsurface is the main wear mechanism for Si/SiC-Ni. Finally the relationships between wear resistance and mechanical properties are discussed.     

Effects of carbon nanotubes on wear of WC/Co micropunches

Punching has potential for mass production of microfeatures. Long lasting punches are critical to successful application of micropunching. This paper is focused on investigating the effects of carbon nanotubes (CNTs) on prolonging the tool life of WC/Co micropunches. CNTs were grown on some of the micropunches. Punching on Ti specimens was carried out using micropunches with and without CNTs. Wear loss and surface texture of the micropunches and the size of the punched holes were measured using confocal microscopy, scanning electron microscopy, digital balance, etc. Results suggested that, with CNTs, a protective layer was formed after the run-in stage. The protective layer could lengthen the useful life of the micropunch by up to 35 % without directly affecting the size of the punched holes.     

Study on relative wear resistance and wear stability of high-speed steel with high vanadium content

In this work, a new concept of wear stability was put forward by authors, and it was quantitatively expressed by factor of wear stability. Different hardness, impact toughness and retained austenite content high-speed steel with high vanadium content samples were obtained by varying heat treatment conditions. The effects of hardness, impact toughness and retained austenite content on relatively wear resistance and wear stability were studied under abrasive wear condition. Results show that relative wear resistance increases with increasing hardness or decreasing impact toughness, whereas the wear stability rises with the increasing of hardness or impact toughness. The analyzing results reveal that mechanical behaviors are only apparent factors to influence wear behaviors. Relative wear resistance substantially depends on retained austenite content (Ar). At retained austenite content of about 30 vol.%, the relative wear resistance is optimal. However, wear stability is scarcely influenced by retained austenite content, which depends on the maximum changing amount of retained austenite under certain condition (ΔAr) in essence. With increasing ΔAr, wear stability linearly decreases.     

Optimization of surface roughness and flank wear using the Taguchi method in milling of Hadfield steel with PVD and CVD coated inserts

In this paper, the Taguchi method and regression analysis have been applied to evaluate the machinability of Hadfield steel with PVD TiAlN- and CVD TiCN/Al₂O₃-coated carbide inserts under dry milling conditions. Several experiments were conducted using the L₁₈ (2 × 3 × 3) full-factorial design with a mixed orthogonal array on a CNC vertical machining center. Analysis of variance (ANOVA) was used to determine the effects of the machining parameters on surface roughness and flank wear. The cutting tool, cutting speed and feed rate were selected as machining parameters. The analysis results revealed that the feed rate was the dominant factor affecting surface roughness and cutting speed was the dominant factor affecting flank wear. Linear and quadratic regression analyses were applied to predict the outcomes of the experiment. The predicted values and measured values were very close to each other. Confirmation test results showed that the Taguchi method was very successful in the optimization of machining parameters for minimum surface roughness and flank wear in the milling the Hadfield steel.     

Abrasive wear resistance of starch consolidated and sintered high speed steel

The abrasive wear resistance of starch consolidated (SC) and super solidus liquid phase sintered (SLPS) M3/2 high speed steel (HSS) samples have been evaluated by a two-body micro-abrasion test (low stress abrasion), using 6 μm diamond abrasive particles, and a three-body abrasion test (high stress abrasion), using significantly larger abrasive particles of blast furnace slag (600 HV) and silicon carbide (2400 HV), respectively. In the tests a commercial powder metallurgical (PM) HSS was used as a reference material.The results show that the microstructure of the SC and SLPS HSS samples is strongly dependent on the sintering temperature used. With increasing temperature the microstructure ranges from a porous (5% porosity) relatively fine grained low temperature sintered microstructure to a fully dense relatively coarse grained high temperature sintered microstructure with eutectic carbides/carbide networks. However, despite the pronounced microstructural differences displayed by the as-sintered HSS microstructures these show a relatively high abrasive wear resistance, comparable with that of a HIPed HSS reference, both under low and high stress abrasion contact conditions. The characteristic features of the low and high temperature sintered microstructures, i.e. the pores and coarse eutectic carbides/carbide networks, only show a limited impact on the wear rate and the wear mode (dominant wear mechanism). The results obtained imply that near net shaped components manufactured by starch consolidation and super solidus liquid phase sintering might be of interest in tribological applications.     

Surface durability of WC/C-coated case-hardened steel gear

The purpose of this study is to investigate the influence of tungsten carbide/carbon (WC/C) coating on the surface durability of casehardened steel gear. Two kinds of WC/C coatings were deposited on the ground gear pair made of chromium molybdenum steel with carburizing and quenching. One is the conventional WC/C coating, and the other is WC/C coating with about 1 μm CrN interlayer. Here, the WC/C-coated test pinion and the WC/C-coated one with CrN interlayer are represented by WT and ST, respectively. Non-coated test pinion is represented by NT. The surface roughness along the tooth profile direction of WT and ST was almost the same as that of NT. A spur gear test was carried out with an IAE power circulating type gear test rig under EP gear oil lubricating condition. The fatal failure mode of the test pinions was pitting due to surface cracking. The fatigue life of WT was longer than that of NT under a maximum Hertzian stress p _max=1700 MPa. On the other hand, under p _max=1900 MPa, that of WT was as long as that of NT due to the peeling occurrence of the coated layer. Under the comparatively low load condition without peeling occurrence, the surface roughness of WT decreased with the increasing number of cycles, and their fatigue life became longer than that of NT. On the contrary, in the case of ST, the peeling of the coated layer occurred at a comparatively early stage of the gear test, and the dedendum was worn by tens of micrometers. Therefore, in the case of ST, the effect of the WC/C coating disappeared at a comparatively small number of cycles.     

Effects of Co content and WC grain size on wear of WC cemented carbide

WC cemented carbides are used extensively to improve abrasion resistance. Co content and WC grain size influence the mechanical properties of the cemented carbides. In this study, the effects of Co content and WC grain size of cemented carbide on wear were examined. We prepared 13 different cemented carbides with different Co content and WC grain size. Wear tests were carried out against 0.45% carbon steel under dry condition at 98 N and 232 mm/s. From the results, we found that wear increased with both Co content and WC grain size. Specific wear rate of the cemented carbides tested was in the range of 10⁻⁷ mm³/(N m). We discussed the wear properties with hardness and the mean free path of the cemented carbide. These two parameters alone cannot explain the wear property.     

Impact collapse characteristics of CF/Epoxy composite tubes for light-weights

This paper investigates the collapse characteristics of CF/Epoxy composite tubes subjected to axial loads as changing interlaminar number and outer ply orientation angle. The tubes are aften used for automobiles, aerospace vehicles, trains, ships, and elevators. We have performed static and dynamic impact collapse tests by a way of building impact test machine with vertical air-compression. It is fanad that CF/Epoxy tube of the 6 interlaminar number (C-type) with 90° outer orientation angle and trigger absorbed more energy than the other tubes (A, B and D types). Also collapse mode depended upon outer orientation angle of CF/Epoxy tubes and loading type as well ; typical collapse modes of CF/Epoxy tubes are wedged, splayed and fragmentcl.