Improvement of wear resistance of components for hydraulic actuators: Dry sliding tests for coating selection and bench tests for final assessment

•Sliding contact in a hydraulic actuator: investigations on thermal spray and DLC coatings.•Ranking of candidate solutions by laboratory dry sliding tests.•Best results by a-C:H DLC with a WC/C interlayer on carburised or plasma-nitrided steel.•Bench tests on best coatings: increase of contact duration from 5 to 22 h.

Alternative coatings/surface treatments for the replacement of the ones currently used in a hydraulic actuator (where sliding motion occurs) were investigated. Candidate solutions were ranked on the basis of laboratory dry sliding tests, followed by bench tests. Thermal-spray coatings were outperformed by a-C:H DLC coatings with a WC/C interlayer, deposited in duplex combinations on carburised or plasma-nitrided steel. The best solution (DLC-coated carburised E470 steel sliding against DLC-coated plasma-nitrided 36CrNiMo4 steel) demonstrated a remarkable increase of contact duration: from less than 5 h in the current configuration, to 22 h without temperature or drain flow increase in the new configuration.

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