Effect of Nitride Layer Thickness on Reciprocating Sliding Wear Behavior of AlN Layers on Spray-Formed Al Alloys

Dry sliding friction and wear behavior of nitrided and non-nitrided spray-formed Al alloys against AISI52100 steel were investigated using a linear-reciprocating ball on flat configuration under different normal loads. In case of nitrided spray-formed Al alloys, an increase in the applied normal load leads to a steady reduction of the stationary stage of the coefficient of friction depending on the sustainability of the AlN/Al compound. With regard to the nitride layer, thickness-specific wear regimes are distinguished for both spray-formed Al alloys. Nitrided spray-formed AlSi alloys show mild abrasive wear independent of normal load in case of AlN layers with up to 3 µm thickness. The layers exhibit an increased wear resistance compared to the non-nitrided condition for all applied test loads. Thick AlN layers > 4 µm show a steep increase in wear rate at loads exceeding 10 N, indicating a severe adhesive wear. These layers fail due to nitride layer delamination. Nitrided spray-formed AlMg alloys show mild abrasive wear for thin AlN layers < 4 µm up to normal loads of 12 N. Thick AlN layers almost immediately fail upon the initiation of the sliding contact due to crack formation within the nitride layer.