Study of surface roughness and hardness of low carbon nickel-chromium based alloy steels under high temperature (AISI sae8630, 3140 & 9310)
High temperature Tribology is an interesting and challenging area which deserves more attention on wear resistance. The present investigation relates to understanding the surface roughness and hardness by the effect of different operational conditions like wear pressure, sliding speed and ambient temperature on AISI SAE 8630, 3140, and 9310. Dry sliding wear tests have been carried out on the materials AISI SAE 8630, 3140, and 9310 under room temperature and also at high temperatures like 200°C, 400°C and 600°C on pin on disc type wear testing machine for 10,000 m sliding distance. The wear tests were carried out under the operational conditions of three sliding speeds like 1, 3 and 5 m/s, under the wear pressures of 0.125 MPa, 0.375 MPa and 0.625 MPa. Weight loss was recorded after each wear test. Hardness after wear was measured by micro hardness tester under 100 gm wear pressure. Roughness of the worn-out surface along the parallel & perpendicular was measured by roughness instrument.
 The present investigation was undertaken keeping in view the wear behaviour of metallic material influenced by the frictional force, which is turn, is governed by the hardness & oxidation kinetics of the mating surface on the high temperature wear. Nickel Chromium based alloys have been reported to be widely used as they combine several advantages such as abrasion, erosion & resistance to high temperature corrosive atmospheres. In this article a brief review of the performance of Nickel Chromium based alloy at different speeds, loads and temperatures has been made and compared with the room temperature.
 It is observed that the hardness of the worn out surface increased with an increase in the load and sliding speed due to work hardening at room temperature. Under low operational conditions, two body abrasive, under high operational conditions oxidative and under moderate operational conditions adhesive wear mechanisms are observed.
Some frictional features associated with the sliding wear of the nickel-base alloy N80A at temperatures to 250 °C
Abstract The time-dependent variations of friction coefficient and the contact resistance of a nickel-base high-temperature alloy, N80A, during like-on-like sliding in pure oxygen at temperatures of 20–250 °C were simultaneously recorded and the tribological behaviour correlated with the nature of the sliding contact. A transition to a positive contact resistance always occurred after some time of sliding in the temperature range investigated. However, the time-dependent variations of coefficient of friction showed quite different features at the various temperatures. Corresponding to the times of the transitions in contact resistance, at 20 °C, the friction coefficient increased to a higher value from the initial value while, at 250 °C, it decreased to a lower value; however, at 150 °C, the coefficient of friction remained unchanged after the transition. Scanning electron microscopy observations have shown that the predominant factor for such different tribological responses at the various temperatures is the nature of the contact between the surfaces. At 20 °C, the real contact areas mainly consisted of loosely compacted particles while, at 250 °C, the load-bearing areas were smooth wear-protective oxide layers. At the intermediate temperature, 150 °C, the load-carrying areas comprised both types of contact. A mathematical model has been proposed and is used to relate the frictional behaviour to morphological features of the wear surfaces developed at the various temperatures.
Liquid state 1H high field NMR in food analysis.
2012 Elsevier B.V. All rights reserved.