Friction And Wear Behaviors Of ZrN Coated Tool Materials

At present, ZrN is attracting special attention as it is a refractory compound with high hardness, high melting point, high chemical and thermal stability. Extensive researches were carried out on its mechanical properties, microstructure stress status and failure mechanisms.ZrN coatings were deposited onto cemented carbide and Zr interlayer using arc ion plating technique. Results showed that the T5 (ZrN/Zr) coating had good mechanical properties. The hardness is 27.78 GPa, the adhesive strength is 70.23 N, the coating thickness is 5.23 μm.Finite element model was established by ANSYS software to get the stress and its distribution during high-speed ring-block wear processes. Results showed that there was a great difference of the maximum of main and shear stress for ZrN coatings. The maximum of main stress was located at the center of sliding couple, while the maximum of shear stress at the outside of sliding couple. The value of the stress increased with the increase of applied load, and the sliding speed just has little effect on the stresses.Dry friction and wear tests at room temperature were conducted with a MRH-3 high-speed ring-block tribometer. Results showed that the friction coefficient and the wear rates of the uncoated tools were higher than ZrN coatings. The friction coefficient of uncoated tools T1 is 0.3899 and the wear rate of T1 is 4.1008(×l0¹⁰cm³/N.m), therefore the friction coefficient of coated tool T5 is 0.1990 and the wear rate of T5 is 1.0406(×10^-10cm³/N.m). The wear rates increased with the increase of the applied load, the friction coefficient decreased with the applied load, the wear rates decreased with the increase of the sliding speed. ZrN coatings were better bonded to YT15 cemented carbide substrate than YG6 cemented carbide substrate under the condition of the same deposition technique. ZrN coatings with Zr interlayer have better friction and wear behaviors than ZrN coatings.ZrN coatings were observed in an SEM during the abrasive wear tests using a ring-block and 45# as counterpart. SEM observations showed that wear mechanisms of ZrN coatings were mostly abrasive wear and bnttleness break off coatings.