Temperature Wear Tester Research Articles

Optical characterization of sputtered a-C:H overcoats: relationship to accelerated wear testing, film composition and substrate temperature

The durability of the protective carbon overcoat for thin film magnetic media is becoming increasingly important due to the decreased head to disk spacing during drive operation (currently approximately 40 nm) and the increased number of contact-start-stop (CSS) cycles required by drive manufacturers (currently approximately 100 000). Due to the increasingly large volumes of thin film magnetic media production, quick and easy methods of monitoring of the carbon overcoat properties are essential. In this work, we report the physical and optical properties of reactive d.c. sputtered a-C:H films and the effect of the substrate temperature and bulk oxygen incorporation on these properties. Optical properties were determined using ellipsometry, an n&k optical analyzer and Raman spectroscopy. Accelerated wear testing was performed in the form of an alumina abrasive tape test. High-resolution secondary ion mass spectroscopy (SIMS) was used to determine the relative concentrations of C, H, O and N in the thin film “bulk”. A relationship was found between the Raman spectra and accelerated wear testing as well as between the bulk oxygen to carbon ratio and accelerated wear testing.

High temperature friction and wear testing of silicon nitride ceramics

This paper describes the results of unlubricated sliding wear tests carried out on ceramics and composites based on silicon nitride. These were silicon nitride, silicon nitride with titanium carbide, and an electrically conductive silicon nitride with titanium nitride. The tests were carried out from room temperature to 1200°C. For all the materials, there was a small increase in friction from room temperature to 300°C, followed by a small decrease as the temperature increased, until a sharp increase in friction coefficient at 1200°C. There was a maximum in wear as the temperature was varied for all materials, with almost no wear at room temperature and at 1200°C. The wear of the silicon nitride material was significantly higher than that of the composite materials at 900°C.

Ion beam etching technique in the preparation of samples for cross-sectional microscopy studies of thin films and hard coatings

The scanning tunneling microscope has proved to be an effective tool in the structure characterization of interfaces and interlayers in thin films and coatings. However, since it lacks the deep profiling capabilities sufficient to penetrate hard coatings, an ion beam etching method has been developed for cross-sectional sample preparation. The sample preparation method is developed keeping in mind the image formation of a scanning tunneling microscope which is based on the topographical differences of the inspected surface. Thus the sample preparation process includes three main parts. Firstly, a mechanical grinding and polishing step, secondly, an ion beam polishing step for producing a smooth surface and, thirdly, an ion beam etching step for producing a topography related to the bulk microstructure of the sample. Examples of results obtained with TiN hard coatings are given, including X-ray scanning force microscopy pictures of a tribofilm grown on a TiN-coated cast iron sample during a high temperature wear test; the usefulness of the developed technique is discussed. The results achieved are compared with the structural information obtained by X-ray transmission electron microscopy analysis from the same samples.

Sliding wear of cast-iron coatings and cast-iron-cast-iron pairs in lubricated contact

The friction coefficients and wear rates of cast-iron coatings and cast-iron-cast-iron pairs in lubricated contact at different temperatures were measured using an elevated temperature wear tester. The removal mechanism of materials and the behavior of coating, substrate microstructure and precipitation particles during wear were studied by scanning electron microscopy and energy dispersive X-ray analysis. It was shown that at higher temperatures the wear of electroplated chromium/niobium cast-iron pair was mainly caused by adhesion, but at lower temperatures the wear was a result of fatigue delamination which was controlled by the nucleation and propagation of fissures. Whether the temperature was high or low, the asperity on the infiltrated niobium layer was observed to cause abrasive wear of the liner.

Effect of microstructure and properties on the high temperature wear characteristics of 3Cr2W8V (H21) steel

The effects of microstructure on the high temperature wear characteristics of 3Cr2W8V steel, the high temperature wear mechanisms and the features of the worn surface have been investigated by means of a resistance-heating high temperature wear-testing device of our own design. It has been shown that the primary parameters affecting the high temperature wear behaviour of the material seem to be the precipitated carbides and austenite grain size in the microstructure, high temperature hardness and oxidation resistance of the material. The optimum high temperature wear resistance of the steel can be obtained by employing suitable quenching and tempering temperatures. The wear test temperature vs. wear value curves for this steel, heat treated using different heat treatment regimes, are similar in shape and different from each other in wear value. However, the wear mechanisms of this steel vary with temperature ranging from room temperature to 700 °C. Although in the range 400–700 °C all the scars are primarily composed of a number of grooves and varying degrees of built-up layered areas, the presence of these layered areas reduces the high temperature wear.

Long-term exposure of plasma-sprayed ZrO 2 in high temperature reactor helium

Plasma-sprayed coatings will be used in future high temperature reactors (HTRs) to help overcome friction and wear problems. Extensive investigations have shown that an air-plasma-sprayed Ni-Cr-Al-Y/ZrO 2-Y 2O 3 duplex coating offers effective protection against thermal shock, non-self-welding, sliding wear, strain tolerance and short-term exposure to HTR helium. A report is given on the response of a duplex coating prepared by reduced pressure plasma spraying (composition as above) to high temperature wear testing and long-term exposure in HTR helium.

熱間工具鋼，耐熱鋼及びステンレス鋼の高温摩耗特性

Using high temperature wear testing machine of direct electrical resistance heating type, an investigation was made on the influence of rotating ring materials and sliding velocities on specific wear, and on the comparison of wear characteristics of hot-work tool steels, heat-resisting steels and stainless steels, and also the effect of gas nitriding upon wear resistance.Specific wear has good correlation with hardness at testing temperatures up to 800°C. SKH9 and SKH55 steels with high hardness have superior wear resistance to SKD5 and SKD61 steels. Specific wear of SKD61 with the rotating ring of SKH9 was 1/30 to 1/5 of that for the spherodizing annealed SCM415 ring.Wear resistance of SKD61 and Max 2 Steels at high temperatures increased considerably after gas nitriding treatment.