Micro-impact testing of AlTiN and TiAlCrN coatings

Abstract

A novel micro-scale repetitive impact test has been developed to assess the fracture resistance of hard coatings under dynamic high strain rate loading. It is capable of significantly higher impact energies than in the nano-impact test. It retains the intrinsic depth-sensing capability of the nano-impact test enabling the progression of the damage process to be monitored throughout the test, combined with the opportunity to use indenters of less sharp geometry and still cause rapid coating failure. The micro-impact test has been used to study the resistance to impact fatigue of Al-rich PVD nitride coatings on cemented carbide. The impact fatigue mechanism has been investigated in nano-and micro-scale impact tests. Coating response was highly load-dependent. A Ti 0.25 Al 0.65 Cr 0.1 N coating with high H 3 /E 2 performed best in the nano-and micro-impact tests although it was not the hardest coating studied. The

Elevated temperature micro-impact testing of TiAlSiN coatings produced by physical vapour deposition

“…In turning Ti6Al4V at 80 m/min the monolayer performed worse at low cutting force (feed rate = 0.1 mm/rev) but at higher cutting force (feed rate = 0.2 mm/rev) larger flank wear and spalling on the rake face was observed for the multilayer TiAlN/TiSiN. In micro-impact an micro-scratch tests of AlTiN and TiAlCrN coatings on WC-Co the coating with highest H 3 /E 2 showed greater chipping outside the impact crater or scratch track [42].…”

“…In the micro-impact test this chipping is accompanied by substrate exposure at the edge of the impact crater and for WC-Co substrate, fatigue damage of the hard WC. In the micro-impact the results are strongly influenced by the coating and the substrate [42]. Figure 7 contrasts the behaviour of these TiAlSiN coatings on ISO P30 with a TiAlCrN monolayer on H10A cemented carbide (previously tested in [42]).…”

“…In the micro-impact the results are strongly influenced by the coating and the substrate [42]. Figure 7 contrasts the behaviour of these TiAlSiN coatings on ISO P30 with a TiAlCrN monolayer on H10A cemented carbide (previously tested in [42]). ISO with 10 wt.…”

“…The maximum energy supplied per impact with the microimpact technique is around 2 orders of magnitude greater than the maximum possible in the nano-impact technique. Nano-and micro-scale tests have been used in the study of the resistance to impact fatigue of Al-rich PVD nitride coatings on cemented carbide [42]. A Ti0.25Al0.65Cr0.1N coating with high H 3 /E 2 performed best in the nano-and micro-impact tests although it was not the hardest coating studied.…”

“…Although experimentally more challenging than at room temperature, nano-and micro-scale mechanical and tribological tests can be performed at elevated temperature. [11,37,38,[42][43][44] High temperature micro-scratch tests have shown that the critical load at 500 C can be larger than at room temperature [11,37].…”