Papers by Keyword: Wear Resistance

Abstract: Thermally sprayed cermet coatings are widely used in many engineering applications to protect against wear and corrosion. In this study, three kinds of (Ti,Cr)C-based powders with 18, 25, 33 wt.% content of Ni binder were deposited onto stainless steel substrates by plasma spraying technique. The microstructure and dry sliding wear resistance of the (Ti,Cr)C-Ni coatings were investigated. The (Ti,Cr)C-Ni coatings have a heterogeneous structure composed of (Ti,Cr)C particles and Ni binder. Fracture and partial dissolution of the (Ti,Cr)C particles were found to occur during the plasma spray process. Among all the tested coatings, (Ti,Cr)C-33wt.%Ni coating exhibits lower wear rates and friction coefficients under all conditions. Worn surfaces of the coatings were analyzed using SEM to investigate the wear mechanism. With the increase in Ni content from 18 up to 33wt.%Ni wear mechanism of the (Ti,Cr)C-Ni coatings changes from abrasive to tribo-oxidation.

Abstract: As a post treatment, thermal remelting is an effective method to eliminate pores and establish a metallurgical bonding for thermal sprayed coatings. However, it is rather difficult to obtain simultaneously high corrosion and wear resistance, since additional energy input usually leads to more homogeneous microstructure in coatings, which deteriorates mechanical hardness. In this work, flame remelting has been imposed to high velocity oxygen-fuel sprayed self-flux NiCrBSi coatings. The remelting effects on microstructure were characterized in terms of porosity and phase analysis. The microhardness, wear resistance and corrosive behaviors were compared among substrate steel, as-sprayed and as-remelted coatings. Results show that the lamellar boundaries and internal defects in the as-sprayed coatings have been eliminated by remelting. The coating porosity has substantially reduced from 7.36% to 0.75%, and a metallurgical bonding at the coating/substrate interface has been formed. Comparing with the as-sprayed coatings, the microhardness of the remelted coatings increases about 21% and the wear weight loss reduces about 42%. By flame remelting, the wear mechanism changes from furrow and abrasive wear to micro-cutting and local fracture. The remelted coatings have also exhibited better corrosion resistance by means of salt spraying and potentiodynamic tests.

Abstract: This study observed the results of plasma nitrocarburizing processes on JIS SKD61 Steel. This research aims to use a plasma nitrocarburizing process to increase the hardness and wear resistance of JIS SKD61Steel. Before plasma nitriding was carried out, the sample had undergone a pre-treatment process. The optimum hardness value obtained after the pre-treatment process was 504 HV. The optimum hardness obtained in the plasma nitrocarburizing sample was 830 HV at temperatures 500°C for 4 hours. The optimum wear resistance or specific wear results on plasma nitrocarburizing was 0.11 x10^-6mm²/kg at temperatures 400°C for 4 hours and 0.08 x10^-6mm²/kg at temperature 500°C for 4 hours. XRD test results show that the phase formed in the nitrocarburizing compound layer was the iron nitride, iron carbonitride FeN, FeN_0.49, ε-Fe_2-3N, or ε-Fe_2-3(N,C). The process of plasma nitrocarburizing has improved the mechanical properties of hardness and wear resistance of SKD61 steel.

Abstract: The experimental results of obtaining complex-alloyed intermetallic alloys by the method of liquid-phase self-propagating high-temperature synthesis (SHS) and their subsequent use for the formation of wear-resistant coatings by the method of electrospark deposition (ESD) are submitted. Metal oxides Cr2O3, NiO, CoO and mineral concentrate containing a larger part of ZrO2 in its composition were used as a melt charge for the SHS experiments. Alloys based on Ni-Al system dopped with Cr, Zr, Co, and C were obtained. It was established that extra addition of C led to the refinement of the alloys microstructure (3-5 times). ESD coatings were formed on steel 45 using the obtained alloys as anode material. The coatings formed by using the alloys doped by Co, Zr, Cr and extra addition of C (0.4 wt%) proved to be maximum wear resistant.

Abstract: The physicomechanical properties and morphology of composite electrochemical coatings (CEC) nickel-cobalt-nanodiamond from a chloride electrolyte-colloid of optimal composition have been investigated. For this CEC, microhardness (21-25 GPa) and internal compressive stresses (150-210 GPa) were determined. The study of wear and the Corrodcoot-test of the CEC showed a higher wear resistance (1,5 times) and the protective ability (2-3 times) of the CEC in comparison with chrome coatings. Studies of the CEC morphology and the nickel-cobalt alloy showed that the roughness of the resulting deposits, in comparison with nickel coatings, is 10 times less, and the fractal dimension of the coating surface is of the greatest importance. The cubic type of the nickel-cobalt-nanodiamond CEC lattice is established. The leveling effect on the structure of galvanic deposits of nanodiamond introduced from outside, as well as of microheterogeneous nickel and cobalt compounds formed in the electrolyte-colloid, has been determined.

Abstract: The present research shows the possibility of using an ytterbium nanosecond pulsed fiber laser for wear resistance improvement of carbon and alloy steels. The wear test was performed in accordance with the block-on-ring scheme with dry sliding friction on a friction machine. Surface dispersing/alloying was carried out from a boron carbide paste. This leads to a significant wear resistance improvement of steels. It was revealed that the mass loss during wear test reduced by several times after laser treatment compared to the non-treated samples. The wear mechanism differs depending on the type of steel and largely refers to their microstructure and composition. The tribo-oxide layer forms during the wear test.

Abstract: The mining industry is the main base of the country's industrial potential, a significant part of which is the development and production of various rocks and minerals. The main type of machines used in open pit mining are powerful excavators, who make up the bulk of the equipment fleet of mining enterprises. Operating enterprises incur large losses due to wear and destruction of excavator bucket teeth, therefore, improving the quality of the tooth material is an urgent task. This article discusses the influence of the casting quality, including the cast structure of the material, on the performance of the excavator teeth. The object of research was the teeth of the buckets of Cat-391 and VOLVO-350 mining excavators made of 30Cr2Si2MnMo steel after long-term operation. The actual condition of the bucket teeth of mining excavators after operation was examined and microstructure, hardness and worn surfaces of the teeth was analyzed. The study showed that the efficiency of excavator bucket teeth is determined by the level of unevenness of the microstructure and microhardness and the presence of defects, hot and cold cracks. It has been established that the main reason for the accelerated failure of the teeth of open-pit excavator buckets is the superposition of various microstructural defects connected with unevenness of the metal microstructure and imperfection of the casting process. Main directions of increasing efficiency of mining excavators’ teeth bucket were identified.

Abstract: Slurry pumps in the mineral processing industry are parts that erode very quickly. Erosion is predominantly caused by abrasion from fine particles of the ores. Because of this, the erosion process takes place on impeller blades and cover plates that directly contact the slurry. This paper evaluates the wear of laser-coated pump parts in the mineral processing industry. Building upon previous research conducted by the authors, we aimed to determine the best laser coating powder system to extend the useful life of specific laser-coated pump parts. Four blades of a slurry pump impeller were each treated with a different laser powder coating, then assessed for wear after 19 days of operation. During this real-life trial, each powder system performed differently. The laser coatings were worn away in two general directions. The first direction was along with the blade pattern, and the second wear direction was from the center of the impeller to the direct blade surface. Partial surface cladding led the material to wear away faster than complete surface cladding due to perpendicular force. Based on these results, in order to use material hardness and wear resistance to higher efficiency, we need to cover all surfaces with different thicknesses depending on the wear rate of the part. This study also showed that Powder System 2 was the most suitable coating material for this type of slurry pump.

Abstract: Several parameters are required to improve Tire dynamic performances like high wet and dry traction (Grip), high wear resistance and high steering performance (handling). These performances depend on the physical properties of tire tread compound, tire construction, tread profile and road conditions. The most influential one is the reinforcing filler, which is responsible for inheriting the tread dynamic properties. Conventionally, carbon black is used as filler but it possesses a major hitch of CO₂ emission during manufacturing as well as in service conditions. Its high rolling resistance is responsible for boosting the carbon footprint of a vehicle. In the past few decades, the focus has been shifting on silica fillers, an emerging technology to develop low rolling resistance tires resulting in low CO₂ emissions thus contributing in the establishment of a healthy eco system. Design of Experiment (DOE) approach is used therefore, sixteen (16) variants of silica based compounds were prepared and properties of silica based samples were compared with that of carbon black compounds (conventional). The results revealed that this emerging silica filler showed promising results in giving the highest possible wet traction and lowest rolling resistance to minimize CO₂ (Greenhouse gas) in the environment.

Abstract: The wear resistance diagram (WRD) is a useful tool for quantitatively estimating the life span of a tribological system in sheet metal forming at different load levels. However, the WRD derived from the authors’ previous research consists merely of scattered points, which make it difficult to reliably estimate the life span and its uncertainties at all load levels. Therefore, a wear resistance curve (WRC) that encompasses the life spans of all load levels is required for a broader scope of application of wear resistance estimation. In this paper, different models for the estimation of the S-N curve describing the fatigue behavior are tested to investigate their applicability in the estimation of wear resistance curves (WRC) in sheet metal forming. WRDs of different tribological systems are investigated and the results of curve fitting are evaluated. Besides the median of the estimated life spans, the WRCs of different confidence levels are also derived quantile calculation to estimate the load dependent uncertainties of tool life spans. Moreover, due to the time-consuming experiments to determine tool life, it is necessary to discuss possibilities for achieving a satisfactory estimation with the smallest possible number of tests. Therefore, the minimal number of tests and the suitable load levels for a satisfactory estimation will be discussed. After the study, several findings have been obtained:Compared to other models, Hwang and Han’s model for estimating fatigue life of composite material shows good applicability and the highest accuracy in estimating the WRC of uncoated tools.In terms of damage development, the fatigue damage of the composite material and the damage caused by wear on uncoated tools have similarities, which explains the applicability of Hwang and Han’s model for the estimation of WRC.Both higher and lower life wear data are the prerequisite for satisfactory wear estimation.