Structure and properties of wear resistance PVD coatings deposited onto X37CrMoV5-1 type hot work steel

Abstract

The paper presents results of the investigation of the structure, mechanical properties and tribological tests of CrN, TiN, TiN/(Ti,Al)N PVD coatings deposited onto X37CrMoV5-1 type hot work steel. Thin hard coatings are today employed in vast number of applications for reducing friction and wear of tools and mechanical components, however there are still big interest to improve tools used in hot-working process e.g. metal die casting, hot extrusion and hot forging as well as glass and plastics processing. The goal of this investigation is to determine usefulness of that coatings type deposition in order to improve wear resistance of tools made from hot work steels. Based on the results of metallographic examinations of microstructure it was shown that TiN, TiN/(Ti,Al)N coatings have compacted, columnar structure while CrN coating has compacted submicrocrystalline structure. According to the observations made after scratch test we found the highest adhesion for CrN monolayer coating and the lowest one for multilayers TiN/(Ti,Al)N coating. Moreover it was found that failure mechanism during scratch test in all investigated coatings begins with multiple spallings located on the scratch edges followed by cracking and total delamination of coating. The wear resistance was investigated by pin-on-disc method performed in room and elevated to 500 °C temperatures. We found that the lowest wear at certain conditions in both room and elevated temperatures shows TiN monolayer coating what can be connected with their good adherence to the substrate materials as well as the highest hardness.