Wear behavior of TiN coated AISI H11 and AISI M7 twist drills prior to plasma nitriding

The present study examines the wear properties of TiN coated AISI H11 substrate and AISI M7 twist drill bits prior to plasma nitriding. To improve the adhesion of the coat and the substrate, plasma nitriding is carried out before the coating process. The wear scratches and friction coefficient of the workpiece surfaces are obtained under different wear test conditions. The metallurgical changes are examined using EDS and SEM techniques. It is found that adhesion of the TiN coat on the workpiece material occurs on the wear sites of the drill bits. Microcracking and fragmentation of the coat does not demonstrate peal-off; in this case, the adhesion of the coat on the base material is considerably good.