Characterisation of PVD-TiN Coated Austempered Ductile Iron: Effects of Nodule Count and Austempering Temperature

D.A. COLOMBO; M.D. ECHEVERRÍA; O.J. MONCADA; J. MASSONE

ISIJ INTERNATIONAL

IRON STEEL INST JAPAN KEIDANREN KAIKAN

Año: 2011 vol. 51 p. 448 - 455

0915-1559

In this work PVD-TiN coatings are deposited on ADI substrates austempered at 280 and 360°C, with nodulecounts varying between 490 and 1 100 nod/mm2. The deposition is performed at 300°C by the arc ionplating technique. The effects of the substrates’ microstructure on the characteristics of the coatings andthe possible changes in ausferritic microstructure owing to the effects of the deposition process are evaluated.The existing phases, preferred orientation, film thickness, hardness, Young’s modulus, surface topographyand adhesion of each coated sample are determined. A metallographic characterisation of the ausferriticmatrices and determination of the retained austenite content are performed before and after deposition.The results obtained indicate that PVD-TiN coatings feature a preferred orientation of (111) planes parallelto the surface and film thicknesses of about 2m m. Knoop hardness is influenced by the substrates characteristics,the values range from 1 700 to 2 100 HK0.015. Nanohardness values are close to 25 GPa, whileYoung’s modulus shows some scattering (323 to 336 GPa). The surface topography is dependent on the microstructureof the substrates and the surface preparation method employed as well as on the depositionprocess used. The adhesion strength quality of the coatings, according to the Rockwell-C adhesion test, canbe related to HF1–HF2 and is affected neither by the hardness differences between the different substratesnor by the nodule count variation. After the coating process, the microstructure of ADI substrates only suffersnegligible changes and the amount of retained austenite decreases slightly.