A practical methodology to select fretting palliatives: Application to shot peening, hard chromium and WC-Co coatings

Considered as a plague for numerous industrial assemblies, fretting, associated to slight oscillatory displacement, is encountered in all quasi-static contacts subjected to vibration. Depending on sliding conditions, cracking or wear damage can be observed. During the past three decades there has been a huge development in surface treatments. Thousands of new surface treatments and coatings are now available. The critical challenge is to evaluate such treatments against fretting loadings. To achieve this objective, a fast fretting methodology has been developed. It consists in quantifying the palliative friction, cracking and wear responses through a very small number of fretting tests. By defining quantitative variables, a normalized polar fretting damage chart approach is introduced. Applied to shot peening, chromium coatings and WC-Co coatings, it demonstrates the potential benefit of a thermal sprayed WC-Co coatin

Letter from K.W. Kubiak to the Headquarters of The Polish YMCA Attached to the Polish 2nd Corps

1946. Letter from K.W. Kubiak to the Headquarters of the Polish YMCA attached to the Polish 2nd Corps on YMCA matters. Dated May 24, 1946.https://digitalcommons.buffalostate.edu/ymcadocs/1084/thumbnail.jp

Behaviour of shot peening combined with WC-Co HVOF coating under complex fretting wear and fretting fatigue loading conditions

This study investigated the fretting and fretting fatigue performance of tungsten carbide–cobalt (WC–Co) HVOF spray coating systems. Fretting wear and fretting fatigue tests of specimens with shot peening and WC–Co coatings on 30NiCrMo substrates were conducted. The WC-Co coating presents very good wear resistance and decreases by more than 9 times the energy wear coefficient (α) under fretting conditions. The tested coating reduces crack nucleation under both fretting and fretting fatigue studied situations. Finally the crack arrest conditions are evaluated by the combined fretting and fretting fatigue investigation. It is shown and explained how and why this combined surface treatment (shot peening and WC–Co) presents a very good compromise against wear and cracking fretting damage

Influence of roughness on ZDDP tribofilm formation in boundary lubricated fretting

Influence of initial surface topography on tribofilm formation in ZDDP lubricated contact was analysed. A small displacement fretting tests with sinusoidal motion were carried out in classical sphere/plane configuration. A range of surfaces with different initial roughness were prepared by milling and grinding processes. Tests were carried out using variable displacement method where amplitude of imposed displacement was gradually increased after every 1000 cycles from 2 to 30 µm. The surfaces after tribological tests were measured by interferometric profiler. Main findings confirm that initial roughness has a significant influence on antiwear tribofilm formation in boundary lubricated contact. Tribofilm form faster and require less energy to activate in case of rough surface obtained by milling process than in case of smooth grinded surface. However, in contact lubricated by ZDDP additive a significant transfer of material occurred from plane to sphere specimen