Preparation And Tribological Behavior Research Of Toughened HfN-based Films Doped With Multi-elements

Transition metal nitrides are widely used in the field of hard protective films due to high hardness,good corrosion resistance and thermal stability.Facing the harsh service environment of coated workpieces,single nitride films usually have brittle failure due to the inability to balance the relationship between hardness and toughness;It is also difficult to match a suitable extended phase to provide lubrication for the anti-friction and wear resistance in a wide temperature range.In this paper,using magnetron sputtering technology,taking Hf N film as the research object,two strategies are used to control the structure and optimize the mechanical and tribological properties:(1)Alloying W and Mo atoms to form miscible ternary systems of Hf-W-N and Hf-Mo-N,studying the formation process of the friction lubrication layer on interface under thermal and mechanical coupling;(2)Introducing Si atoms to construct nc-Hf(Mo)N/a-Si₃N₄films,to achieve strengthening and toughening by the nanocomposite structure of the crystallines embedded in amorphous matrix.The results show that as W atoms continuously dissolve into the Hf N lattice,the film maintains the FCC single phase structure.Hf_0.27W_0.73N film obtains high hardness(35.3 GPa),enhanced toughness(3.50 MPa�m^1/2)and high H³/E²value(0.71 GPa)because of the solid solution strengthening,which effectively resists crack propagation and brittle failure.The friction coefficient and wear rate values are as low as 0.42 and 8.12�10^-6mm³/N m due to the tribochemical reaction generates easy-to-shear WO₃phase at 400?.The Hf_1-xMo_xN_yfilms with different Mo contents all maintain the substitutional solid solution.When x=0.56,the film reaches high hardness(36.6 GPa)and H³/E²value(0.60 GPa),which are increased by 62%and 147%respectively compared with Hf N,indicating that the resistance to plastic deformation is significantly improved.At 400?,the dense and continuous oxide layer Magn�li phase on the wear surface brings lubrication,which stabilizes the friction coefficient and wear rate at 0.43 and 8.06�10^-6mm³/N m.Due to superior structural stability,Hf_1-xMo_xN_yexhibits lower friction(0.52)and better wear resistance(16.1�10^-6mm³/N m)than those of Hf_1-xW_xN_yfilm at 600?.On the basis of research the Hf-Mo-N,the single phase transforms into nc-Hf(Mo)N/a-Si₃N₄composite structure through doping with Si atoms.Under the synergistic effect of solid solution strengthening,fine grains and interface strengthening,the film with 5.4at.%Si content obtains high hardness(38.6 GPa)and H³/E²value(0.73 GPa).The enhancement of fracture toughness(3.60 MPa�m^1/2)depends on a certain thickness of the amorphous layer to hinder crack propagation.High hardness and toughness enable the film to achieve low friction coefficient(0.37)and wear rate(1.8�10^-6mm³/N m).