Improvement of wear resistance of hot work steels by PVD coatings deposition

The paper presents results of structure, phase composition, tribological and adhesion investigations of wear resistance PVD coatings TiN, TiN/(Ti, Al)N and CrN types deposited in ion plating PVD process onto X37CrMoV5-1 type hot work tool steel. The X-ray quantitative phase analysis makes it possible to find out the preferential crystallographic orientation (111) for the monolayer TiN coating and for the multilayer TiN/(Ti, Al)N one. The diffraction line broadening in case of the CrN coating attests to occurrence of strong internal stresses or to small sizes of its constituent crystallites. It was found that failure mechanism during the scratch test in all investigated coatings begins with multiple spallings located on the scratch edges followed by cracking and total delamination of coating. Regarding to the coating types different location of such damages and loads typical for them can be seen. According to those observations we found that highest adhesion among investigated coating present, CrN monolayer coating and the lowest one for multilayers TiN/(Ti, Al)N coating. The wear resistance was investigated by the pin-on-disk method performed at the room temperature and the one elevated to 500°C. We found that the lowest wear in to fixed investigation conditions in both room and elevated temperatures show TiN monolayer coating. Additionally, one can see that TiN coatings application improves wear resistance for about five times.