Low temperature tribometers and the behaviour of ADLC coatings in cryogenic environment

This paper aims to present the effect of specific operational factors (temperature and humidity) on the selected mechanical properties of a conveyor belt The tests were conducted in a climatic chamber, simulating the effect of both minus and plus temperatures −30 °C to 80 °C (243 K to 353 K) at specific humidity, and in a thermal shock chamber where a varying number of ageing cycles was applied for a specific range of thermal shocks Six different tests in the climatic chamber and four different tests in a thermal shock chamber were conducted The results of the climatic chamber tests demonstrate that many strength parameters have undesired values at a temperature of 10 °C (283 K) and 80 °C (353 K) at a relative humidity of 80% Interestingly, the results revealed that tensile strength, tensile modulus and yield strength are higher at below 0 °C temperature than at above 0 °C temperature For example, comparing the temperature −30 °C (243 K) and +30 °C (303 K) obtained a difference of tensile modulus of nearly 10%, and comparing the temperature −30 °C (243 K) and +10 °C (283 K) the differences were 22%

https://www.mdpi.com/2076-3417/10/12/4201/pdf

Investigation of the Effect of Operational Factors on Conveyor Belt Mechanical Properties

The stability of a series of sulfated zirconia catalysts, promoted with up to 2 wt% iron or manganese, in their calcined state was investigated. Phase composition, nature of surface sulfate species, degree of hydroxylation, and butane isomerization activity changed during aging over months in various atmospheres and during milling. The metastability of small oxide particles is discussed, including literature data on alumina, titania and other oxides. Catalytically active fractions of a material easily transition into more stable, less active forms.

/pdf/the-balance-between-reactivity-and-stability-of-modified-3gtdlmu3lz.pdf

The Balance Between Reactivity and Stability of Modified Oxide Surfaces Illustrated by the Behavior of Sulfated Zirconia Catalysts

Camshaft is one of the key parts or components in the engines of automobile and other vehicles. Due to the cyclic impact loading on the contacting surfaces of the cam and the follower, it often gives rise to premature wear of cam profile and affects a routine run of the valve gear such as the rotational speed, valve displacement and the torque. The objective of this work was to study experimentally the residual stresses at the surface layer of induction hardened cylindrical specimens. The diesel engine camshafts are generally made by EN19 Steel material. However, EN19 steel material has low wear resistance and its service life is shorter. ReplacingEN19 steel with EN41B steel. The results obtained from hardness test indicated that the hardness of the Nitride steel EN 41B is 31% higher than EN19 Steel before induction hardening and the hardness of the Nitride steel EN41B is 45% higher than EN19 steel after induction hardening. Impact test indicated that the toughness of Nitride steel EN41B is 38% higher than EN19 steel.

http://inpressco.com/wp-content/uploads/2014/02/Paper29162-167.pdf

Analysis of Mechanical Properties of En19 Steel and En41b Steel Used In Diesel Engine Camshaft

Friction systems running in cryogenic environment are critical in respect to wear and frictional heat generation because in this temperature range, conventional lubricants can't be applied In order to test the friction and wear behaviour of appropriate solid lubricants and wear resistant material combinations in cryogenic environment, including liquid hydrogen, special test rigs have been constructed These devices provide test conditions for tribological investigations at temperatures ranging from 42K to room temperature in liquid or gaseous environment at pressures between 10-3 mbar and 20 bar Investigations on polymers, composites and metals with and without coatings show that there is a broad variety of appropriate materials for cryogenic friction units, but the behaviour of austenitic steels in such systems gives an example of non sufficient knowledge in this field

Low temperature tribology at the Federal Institute for Materials Research and Testing (BAM)

In cryogenic devices frictional systems often generate undesired heat and experience high wear. Because conventional lubricants cannot be used in this temperature range, solid lubricants or materials with good frictional properties in unlubricated operation are applied. This paper deals with the test rigs for such materials and the results of measurements on polymersteel-couples and amorphous carbon coatings in the temperature range between 10 K and 77 K.

Kryotribologie : Reibung und Verschleiss bei Temperaturen unter 100 K messen

Publisher Summary
In cryogenic environment components with interacting surfaces in relative motion (tribosystems) like beatings, seals and valves cannot be lubricated conventionally by using oils or greases. Therefore, they are critical in respect to wear and frictional heat generation. To obtain reliable data of the properties of conventional and advanced materials in cryogenic tribosystems, model wear tests at low temperatures are performed. Tests with polymer-steel couples verified that some polymers have a favorable tribological behavior at low temperatures. Coatings of amorphous carbon are on principle suitable for cryogenic tribosystems, but their behavior depends strongly on the composition and deposition method. The results of the tribological model tests of polymers show that the basic wear mechanisms of polymers, deformation and adhesion, are still acting at low temperatures but the increasing mechanical strength give rise to a reduced wear. Tests with hard carbon coatings show that they are appropriate for tribosystems in cryogenic environment. Temperature dependent low and high friction states show that further investigations on this material are necessary.

Wolfgang Hübner

Papers

Low temperature tribology at the Federal Institute for Materials Research and Testing (BAM)

Kryotribologie : Reibung und Verschleiss bei Temperaturen unter 100 K messen

Friction and Wear Testing at Cryogenic Temperatures