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The aim of this study was to research the problem of wear localized on the thread joint of a percussive rock drilling tube. Wear of the thread joint causes a decrease in the tightness of the joint and increases the sensitivity of the tube to breakdown.The effect of wear of the thread joint on the endurance of a drilling tube was studied using failure follow-up. As a result of failure follow-up, it...
Multiplated electrical contacts often undergo repeated dynamic loading. In the present study, a pivotal hammering impact wear tester was used to inflict wear scars on typical layered contact configurations. The wear life was observed to consist of three main stages: the plastic deformations stage; the zero wear stage; the measurable wear stage. Experimental observations of the wear behavior aided...
Dynamic impact wear conditions, i.e. contacts in the presence of high cyclic local loads, provide a very demanding wear situation, which occurs in a number of applications, e.g. in interrupted machining or impact contacts between machine parts. Thus, protective coatings for these conditions and methods for their evaluation are currently being pursued by several laboratories. Magnetron sputtered composite...
The characteristics of impact wear of high hardness steel have been studied by repetitive impact testing. The subsurface microstructure and wear debris have been investigated, and both wear resistance and failure models are discussed. Experimental results indicate that there are two zones beneath the wom surface (WS): namely a white layer (WL) and a deformation zone (DZ). The WL is an intensely deformed...
In order to simulate the wear of the valves and valve seat inserts of automotive engines, impact wear tests were conducted using rings made of a JIS SUH36 steel valve material and disks made of a sintered alloy valve seat insert material. Test conditions were as follows: impact energy of 0.588 J, dry air of room temperature, 200°C and 400°C, and sliding speeds of 0-0.8 m s -1 . Under...
A Delrin disc is used in the Bjork-Shiley tilting disc heart valve, where dynamic contact occurs between metallic cylindrical struts and the disc, during valve action. To investigate the wear behavior of the Delrin disc, impact wear tests were performed by using a pivotal hammer device with a spherical striking face. For the biomedical wear study (Milligan et al.), raised temperature (36.6 °C) and...
Surface white-etching layer, subsurface white-etching layer and deformed band were observed in specimens of low alloy steels after impact wear. A narrow bright band can occur in the white-etching layer when the specimen is impacted repeatedly. It is found that most cracks in the impact specimens are confined to white-etching layers. The impact wear resistance of materials is influenced greatly by...
Three kinds of Cr 3 C 2 -25%NiCr coatings prepared by APS-Ar/H 2 , APS-Ar/He and HVOF spraying, respectively, have been studied with a self-made impact wear rig. The wear resistant performances of Cr 3 C 2 -25%NiCr coatings were tested under different impact stress. The wear losses and worn surface profiles are measured, and the corresponding wear mechanisms...
After being impacted in an impact wear tester simulating the conditions in a mill, the surface white layer and internal white adiabatic shear band were observed in a low alloy steel (0.40% C-0.85% Cr-1.55% Ni-0.20% Mo). It was found that cracks can easily nucleate and propagate in the surface white layer and internally formed adiabatic shear band during impact wear processes. Surface white layers...
Adiabatic shear banding (ASB) is an important phenomenon in high energy impact wear. Some factors influencing ASB, such as number of impacts, nature of the abrasive particles and material microstructure were investigated in this paper. It is shown that low alloy steels (40Cr and 40CrNiMo) tempered below 500°C are liable to produce white ASBs whereas specimens with austenitic structure do not readily...
The specifications for a reliable laboratory testing for grinding ball materials still remain a problem in view of the large number of parameters to be reproduced and of the combined effect of impact, abrasion and corrosion wear. A laboratory-scale three-body impact-abrasion testing machine has been built, which uses real ore as abrasive in dry or wet conditions and which is capable of producing impact...
This study addresses the influence of grinding-induced roughness, subsurface damage and residual stress on the repeated impact behavior of silicon nitride, a leading material for diesel poppet-valves. A ball-on-flat repeated impact tester was used to evaluate the impact wear of GS-44 silicon nitride coupons machined in three different conditions: coarsely ground (with 80-grit wheel), finely ground...
A new hammer-mill type impact wear testing facility was built for impact wear testing and characterization. Tests with the hammer-mill impact wear device were carried out on conventional wear resistant materials such as Mn-steels of different compositions, white cast iron, and on new P/M+HIPed wear resistant materials. To verify the validity in using this laboratory wear testing apparatus, wear behavior...
Impact assessment for laser hardened hypoeutectoid 2Cr13 martensite stainless steel was carried out on a specifically developed ball-on-flat impact tester. Results showed better impact behavior of 2Cr13 surfaces treated by a continuous wave CO 2 laser than those under conventional heat treatment. Micro-hardness measurement demonstrated that the surface hardness of the laser treated specimens...
Impact wear was carried out for annealed AISI1045 steel in this study. With the impact frequency of 600 times per min, an 8.29kN impact load was applied on the constant contact area of 540.08mm 2 at the individual attack angles 60° and 90°. The microstructure of white layer for annealed AISI1045 steel was examined by SEM, TEM and HRTEM. It was found that nano structures with ferrite and cementite...
Fretting wear of a vibratory tube is studied from the investigation of the slipping characteristics on the contacts between the tubes and the supports. The primary application of the present research is the tube bundle structures subjected to a flow-induced vibration in the nuclear power plant components. Tests were carried out to simulate the vibration of the fuel rods, in particular, those supported...
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...
Wear problems are consistently arising as a result of the introduction of new or alternative materials to situations where components are impacting.Impact wear has generally not been studied as extensively as other wear mechanisms and as a result information on the causes and actual impact wear data is quite scarce. There are also few impact modelling techniques and those that exist have not been...
The problem of the fatigue strength of wear resistant materials is significant both from the theory and practical point of view. In abrasive wear two different mechanisms of material removal occur either separately or simultaneously. At abrasion and low-angle abrasive erosion, microcutting is dominating and the main criterion for materials selection is hardness. At abrasive impact wear and high angle...
Accurate prediction of fretting wear of heat exchanger tubes is critical for safe and economical operation of nuclear power plants. The ‘work rate’ parameter is commonly used to correlate wear losses to the integral effect of the contact load and the relative sliding distance between the tube and its support. The wear rate-work rate relationship is not unique, strongly dependent on the tube orbital...
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