Jeffrey A. Hawk

The abrasive wear of sintered titanium matrix–ceramic particle reinforced composites

Particulate (TiC, TiB2 or Si3N4) reinforced Ti composites were produced by vacuum sintering (at 1400°C for 2 h). Ti+TiC composites could be sintered to high fractional densities (>93%), even at high TiC loadings (e.g., 40 volume percent (vol%)). No reactions were observed to occur between the Ti and TiC. By contrast, the Ti and TiB2 and Ti and Si3N4 reacted to form composites consisting of Ti, TiB and TiB2 and α-Ti(N), Ti5Si3, Ti3Si, and Ti2N, respectively. As a consequence, Ti was consumed and/or the reaction products intrinsically generated porosity during sintering. These composites were more difficult to consolidate via solid state sintering, particularly at higher volume fractions. Despite the porosity, the composites were more wear resistant (pin-on-drum abrasive wear against 100 μm garnet particles) than unreinforced Ti, with the exception of the Ti+2.5 vol% TiB2 and Ti+≤10 vol% TiC composites. The ranking of microhardness and abrasion wear resistance of the composites was as follows: (hardest, most wear resistant) Ti+Si3N4 (i.e., α-Ti(N), +Ti5Si3, Ti3Si, and Ti2N)≫Ti+TiB2≫Ti+TiC (softest, least wear resistant). The microhardness coupled with the apparent strength of the chemical interface that developed between the constituent composite phases was responsible for the observed wear behavior.

Abrasive wear of intermetallic-based alloys and composites

In this study, the abrasive wear behavior of Fe3Al, TiAl, Ti3Al, Al3Ti, NiAl, Ni3Al and MoSi2, and composites based on these compounds, were assessed and compared to the behavior of selected metals, alloys and ceramics. Under the wear conditions used for these tests, the softer intermetallic compounds (e.g. TiAl and Fe3Al) behaved in a manner similar to the metals and alloys, whereas, the harder intermetallic compound (i.e. MoSi2) behaved more like a ceramic. The influence of Al atomic fraction, superlattice structure and ternary alloying additions on the wear behavior of Fe3Al was investigated. Controlling the Al content and third element additions affected wear resistance more than superlattice structure. Composite strengthening was also explored as a method for improving wear resistance. The addition of hard second phase particles (i.e. TiB2 to NiAl and SiC to MoSi2) was also very effective improving wear resistance. Surprisingly, the addition of softer Nb particles did not significantly degrade the wear resistance of a MoSi2 matrix, even at Nb additions of 40%.

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.

Microstructure and abrasive wear in silicon nitride ceramics

It is well known that abrasive wear resistance is not strictly a materials property, but also depends upon the specific conditions of the wear environment. Nonetheless, characteristics of the ceramic microstructure do influence its hardness and fracture toughness and must, therefore, play an active role in determining how a ceramic will respond to the specific stress states imposed upon it by the wear environment. In this study, the ways in which composition and microstructure influence the abrasive wear behavior of six commercially-produced silicon nitride based ceramics are examined. Results indicate that microstructural parameters, such as matrix grain size and orientation, porosity, and grain boundary microstructure, and thermal expansion mismatch stresses created as the result of second phase formation, influence the wear rate through their effect on wear sheet formation and subsurface fracture. It is also noted that the potential impact of these variables on the wear rate may not be reflected in conventional fracture toughness measurements.

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.

Abrasive wear behavior of NiAl and NiAl-TiB2 composites

Abstract Abrasive wear of NiAl and NiAl with 10, 20, and 40 vol.% TiB 2 has been investigated using particles of different types and sizes. The addition of TiB 2 as a particulate reinforcement to NiAl increases the hardness of the composite with respect to NiAl, and reduces the wear rate at all volume fractions on garnet and Al 2 O 3 abrasives. Abrasion on SiC resulted in a minimum of the wear rate for the composite with 20% TiB 2 for most conditions. The composite with 40% TiB 2 consistently exhibited wear rates higher than the other composites when abraded on SiC. The only instance when the NiAl–40% TiB 2 composite had a lower wear rate was when it was abraded on 16 and 37 μm SiC particles. The NiAl–TiB 2 composite serves as a model system for studying the effect of reinforcement volume fraction on composite wear behavior and is discussed in terms of a composite wear model developed by Axen and Jacobson.

Abrasive wear properties of Cr-Cr3Si composites

Abstract A series of composites based on the Cr–Cr 3 Si system, and containing between 50 and 100%Cr 3 Si, were fabricated by hot pressing. These composites have high stiffness, good thermal conductivity, excellent chemical resistance, and high temperature creep and oxidation resistance, making them potential candidates for hard-facing applications and cutting tools in harsh environments. In this study, the Cr–Cr 3 Si composites were abrasion tested at ambient temperatures in order to evaluate their wear properties. Single scratch tests were performed to give insight into material removal mechanisms. Although like most metal silicides, these materials behave in a brittle manner, the results of this study indicate that the addition of a ductile second phase (Cr) can enhance both their fracture toughness and abrasive wear resistance. The addition of 10% of the rare earth oxide Er 2 O 3 improves the density of the composite, but has no apparent influence on the wear resistance.

Abrasive wear behavior of a brittle matrix (MoSi2) composite reinforced with a ductile phase (Nb)

The toughness of a variety of brittle ceramic and intermetallic matrices has been improved through the incorporation of ductile metallic reinforcements. In these composites resistance to catastrophic failure of the matrix is derived through a combination of mechanisms, including matrix crack bridging, matrix crack defection and rupturing of the ductile phase. The degree to which these mechanisms operate is a function of composite microstructure. In general, the ductile phase is softer than the matrix phase. This may have unique implications when the materials are subjected to a wear environment, whether intentional or not. Hence, it is important to understand the wear behavior of these new materials. MoSi2–Nb was selected as a model composite system, in part because of the wide body of open literature regarding this system. The influences of abrasive wear environment and the composite microstructure (Nb reinforcement size, shape and volume fraction) on the wear resistance of the composites are reported.

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.

An overview of corrosion - wear interaction for planarizing metallic thin films

Corrosion-wear interactions play a very crucial role in developing many technological processes. One of them is chemical-mechanical planarization (CMP) of metallic thin films for manufacturing semiconductor devices such as computer chips. In this paper, we present research approaches undertaken in developing CMP for different metallic thin films, such as tungsten and copper in aqueous media. Mechanisms of material removal during CMP are presented. The role of corrosion, wear, and their synergistic effect are explained. The importance of constructing corrosion-wear maps for these complicated tribo-corrosion-metallic thin film systems is addressed. The application of corrosion-wear maps in developing reliable CMP slurries and processes is discussed.