Bernard Criqui

Zero wear concept using bionotox and polymer‐free engine oils with triboactive materials

Purpose – The purpose of this paper is to underline the future need for OEMs to receive lowSAP, polymer‐ and metal‐free engine oils with high‐viscosity indices and to illuminate for other OEMs the technical feasibility for application of alternative engine oils based on esters or blends of hydrocarbons with esters or polyglycols.Design/methodology/approach – The strategic goal depends technically on the use of intrinsic properties of alternative base fluids, thus substituing some additives, like anti‐wear, extreme pressure and viscosity index improvers. The prone wear resistance of novel triboactive/‐reactive materials enables higher portions of mixed/boundary lubrication generated by oils with a lower viscosity.Findings – Overall, the different bionotox and low‐ash prototype engine oils with reduced additive contents displayed isoperformance regarding the tribological behaviour against cast iron and triboreactive materials. APS‐Tin−2Cr2O2n−1 displayed an overall wear resistance comparable with grey cast ...

Welding for the aluminium car body with high-power Nd:YAG lasers (up to 6 kW)

The use of aluminium alloys is increasing in the automotive industry and the appearance in recent years of high-power Nd:YAG laser sources enable of welding these materials arouses the interest of car manufacturers [1-7]. This paper presents some general overviews of different applications, which are developed yet by CLFA for RENAULT: hood, space frame, structural parts. Some 5000 / 6000 / AS7G welds have been examined and the main results are presented briefly.The use of aluminium alloys is increasing in the automotive industry and the appearance in recent years of high-power Nd:YAG laser sources enable of welding these materials arouses the interest of car manufacturers [1-7]. This paper presents some general overviews of different applications, which are developed yet by CLFA for RENAULT: hood, space frame, structural parts. Some 5000 / 6000 / AS7G welds have been examined and the main results are presented briefly.

Elaboration of AlSn alloys by an Nd:YAG laser beam: tribological characterization

Laser cladding of AlSn alloy onto a mild steel have been carried out. The laser source was a continuous Nd-YAG. Due to similar boiling temperatures of feeding materials, cladded layers are free from porosity. Microstructural analyses show that aluminum and tin do not mix, except at the eutectic composition of 97% of tin. Eutectic compounds are shown. Direct cladding onto the steel produces intermetallic AlxFey layer. This layer is very hard. In order to avoid the formation of this layer, the steel can be pre-coated with nickel. Tribological behavior of the cladded layers is then analyzed, in comparison with an industrial material. Experimental Stribeck curves are plotted. It is shown that lubrication regimes do not change from industrial to laser cladded material. Running in behavior is tested. Results show that a tin layer on the surface of the AlSn laser alloy improve this running in behavior.