Joseph Tylczak

Wear of titanium carbide reinforced metal matrix composites

Abstract The wear resistance of eight titanium carbide (TiC) reinforced metal matrix composites was investigated under different wear conditions. The TiC particles were dispersed in various steel and nickel matrices using a powder metallurgy (P/M) technique. Volume fraction of TiC particles in these composites varied between 0.35 and 0.45. The microstructure of each material was characterized using scanning electron microscopy (SEM), light optical microscopy, and X-ray diffraction (XRD). A high-stress abrasion test (pin abrasion), a low-stress abrasion test (dry-sand/rubber-wheel (DSRW)), an abrasion–impact test (impeller-in-drum) and an erosion test were utilized to understand the wear behavior of these materials under different conditions. While in the low-stress abrasion environment, finer TiC particles (with smaller interparticle spacing) provided better wear resistance, the coarser TiC particles were more effective in protecting the softer matrix from abrasion in the high-stress environment. On the other hand, variation in TiC size did not affect the rate of material loss in the impact–abrasion test. Erosion rate was unchanged with hardness of the composites.

Laboratory abrasive wear tests: investigation of test methods and alloy correlation

Abstract When screening materials, laboratory abrasive wear testing is a quick and inexpensive way of obtaining large quantities on information on wear rates and wear mechanisms. Typical laboratory abrasive wear tests approximate two- and three-body abrasion. The Albany Research Center, however, uses a suite of four laboratory abrasion, gouging–abrasion, and impact–gouging abrasion wear tests to rank materials for wear applications in the mining and minerals processing industries. These tests, and the wear mechanisms they approximate, are: (1) dry-sand, rubber-wheel (three-body, low-stress abrasion); (2) pin-on-drum (two-body, high-stress abrasion); (3) jaw crusher (high-stress gouging-abrasion); and (4) high-speed, impeller–tumbler (impact–abrasion). Subsequently, candidate materials can be ranked according to their performance for each of the wear tests. The abrasion, gouging–abrasion, and impact–abrasion test methods are described, highlighting the predominant wear mechanisms for each test. Data on a wide variety of irons and steels are presented with relative ranking of the materials according to the specific wear test.

Wear of Cast Chromium Steels With TiC Reinforcement

Wear resistance of a series of new titanium carbide reinforced cast chromium steels was investigated under various wear conditions. The steels which were melted in a vacuum induction furnace contained 12 Cr, 3-5 Ti, 1-2 C in weight percent. Microstructure of these materials was characterized using scanning electron microscopy, light optical microscopy, and X-ray diffraction. Microstructure of steels consisted of TiC phase dispersed in a martensitic matrix. High-stress and low-stress abrasion tests, and an erosion test, were utilized to understand the wear behavior of these materials under different environments. The steels were tested in as-cast and heat treated conditions. Wear rates of the cast Cr/TiC steels were compared to those of an AISI type 440C steel and P/M composites reinforced with TiC.

A comparison of laboratory abrasion and field wear results

In the ongoing battle on wear, laboratory tests have been one tool used to evaluate and model the process of wear. A second, less commonly used tool is field wear testing. Field wear testing, while being more time-consuming, has the advantage that the materials are exposed to the actual environmental conditions and abrasives responsible for the wear loss. This paper examines four different abrasive wear tests (pin-on-drum, dry-sand rubber-wheel, jaw crusher, and impeller-in-drum), and compares the results obtained from these tests with field wear tests using the Albany Research Centers Planar Array Field wear test. A variety of ferrous-based alloys commonly used to resist abrasion in the mineral processing industry were tested, including carbon steels, low alloy steels, austenitic steels, and white cast iron.

Solid particle erosion behavior of an Si3N4-MoSi2 composite at room and elevated temperatures

The solid particle erosion behavior at room and elevated temperatures (180, 500, 700 and 900 C) of an Si[sub 3]N[sub 4]-MoSi[sub 2] composite was studied. Alumina particles entrained in a stream of nitrogen gas impacted the target material at a velocity of 40 m/s. Impingement angles of either 60, 75 or 90[degree] were used. It was found that the erosion rate for the Si[sub 3]N[sub 4]-MoSi[sub 2] composite (measured at room temperature) was a maximum at the 90[degree] incident angle, erosion behavior typical of brittle materials. The erosion rate of the composite at a 75[degree] impingement angle increased slightly with increasing test temperature up to 700 C (i.e. from 4.1 to 4.9 mm[sup 3]/g). At 900 C, the measured erosion rate decreased to 2.9 mm[sup 3]/g. The erosion behavior of the Si[sub 3]N[sub 4]-MoSi[sub 22048mposite was compared to that of commercially available Si[sub 3]N[sub 4], WC-6%Co, 304 SS, IN-800 (Ni-Fe-Cr alloy) and Stellite-6B (Co-Cr-W-Mo alloy).

A large-scale impact spalling test

Abstract A unique test apparatus is described that effectively produces spalling on wear-resistant alloys and can be used to study the causes of spalling. The work was conducted by the U.S. Department of the Interior, Bureau of Mines, as part of an effort to minimize the consumption of strategic materials used during the mining and processing of minerals. The test utilizes balls 75 mm in diameter made of the test alloys, which are dropped a distance of 3.5 m. Multiple impacts over a range of energy are produced between the balls. The unique design of the test apparatus provides a multiplying effect that results in 30 000 or more total impacts per hour on 20 or so test alloys. The four major types of failure that were observed on 22 commercial and experimental alloys that received up to 300 000 impacts are discussed.

Fractal characterization of wear-erosion surfaces

Wear erosion is a complex phenomenon resulting in highly distorted and deformed surface morphologies. Most wear surface features have been described only qualitatively. In this study wear surfaces features were quantified using fractal analysis. The ability to assign numerical values to wear-erosion surfaces makes possible mathematical expressions that will enable wear mechanisms to be predicted and understood. Surface characterization came from wear-erosion experiments that included varying the erosive materials, the impact velocity, and the impact angle. Seven fractal analytical techniques were applied to micrograph images of wear-erosion surfaces. Fourier analysis was the most promising. Fractal values obtained were consistent with visual observations and provided a unique wear-erosion parameter unrelated to wear rate.

Wear Evaluation of High Interstitial Stainless Steels

A new series of high nitrogen-carbon manganese stainless steel alloys are studied for their wear resistance. High nitrogen and carbon concentrations were obtained by melting elemental iron-chromium-manganese (several with minor alloy additions of nickel, silicon, and molybdenum) in a nitrogen atmosphere and adding elemental graphite. The improvement in material properties (hardness and strength) with increasing nitrogen and carbon interstitial concentration was consistent with previously reported improvements in similar material properties alloyed with nitrogen only. Wear tests included: scratch, pin-on-disk, sand-rubber-wheel, impeller, and jet erosion. Additions of interstitial nitrogen and carbon as well as interstitial nitrogen and carbide precipitates were found to greatly improve material properties. In general, with increasing nitrogen and carbon concentrations, strength, hardness, and wear resistance increased.

High-temperature stability of silver nanoparticles geometrically confined in the nanoscale pore channels of anodized aluminum oxide for SERS in harsh environments

We report the ability of nanoscale pore channels of anodized aluminum oxide (AAO) to endow entrapped silver nanoparticles (Ag NPs) within with structural and oxidation stability for potential surface-enhanced Raman scattering (SERS) at elevated temperatures. AAO was prepared via two-step anodization of high purity aluminum foil in phosphoric acid. Ag NPs of controlled size and coverage were obtained via in situ seeded growth from aqueous AgNO3 solution inside the AAO pore channels. The structural and chemical characteristics and the SERS activity of the Ag NPs before and after environmental exposure in air at up to 600 °C for as long as 5 days were evaluated using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. We show that the Ag NPs entrapped in the AAO pore channels exhibit enhanced structural and oxidation stability and thus retain significant SERS activity upon high-temperature treatment, indicating the intricate role of geometric confinement in retarding Ostwald ripening, evaporation loss, as well as oxidation of Ag NPs.

A study of the abrasive wear of pure metals using a pin-on-drum apparatus☆

Abstract As a part of an investigation of the mechanisms of abrasive wear, the Bureau of Mines, U.S. Department of the Interior, has made a further study of the proposed linear relationship between abrasion resistance and hardness for pure metals, using samples of known purity and grain size. Two different types of abrasive cloth were used for the tests and were found to have little effect on results. It is further demonstrated that abrasion resistance usually correlates better with the hardness of worn or otherwise work-hardened specimens than with the hardness of unworn, annealed specimens, and that the correlation improves when it is restricted to metals of the same crystal structure. The present results are in reasonable agreement with those of previous studies.