Study Of Nc-B₄C/a-Ti And Nc-B₄C/a-Si₃N₄Nanocomposite Coatings Prepared By Multi-target Magnetron Co-sputtering

This paper reported the design and synthesis of nc-B4C/a-Ti and nc-B4C/a-Si3N4nanocomposite coatings on Si (100) and stainless steel by multi-target co-sputtering system. The mechanical properties of the nanocomposite coatings including hardness, elastic modulus and adhesion were measured by profiler and Nano Indenter XP system. X-ray diffraction (XRD) and transmission electron microscope (TEM) were employed to investigate crystal structure of the coatings. Chemical composition and binding energy of the coatings were obtained by X-ray photoelectron spectroscopy (XPS). Our aim is to obtain insight into the significance of different process parameters on the structure and mechanical properties of the nanocomposite coatings. The nanocomposite coatings with high hardness, fracture resistance, low friction coefficient and good thermal stability can be synthetized by controlling process parameters during deposition.Nanocomposite nc-B4C/a-Ti coatings were synthesized on Si(100) wafer and stainless steel substrates from Ti target and B4C target respectively by Multi-target Magnetron Co-sputtering. Extensive measurements were taken to investigate the influences of the deposition temperature and work pressure on microstructure, hardness, elastic modulus, residual stress, friction coefficient, and adhesion strength. XRD patterns showed the nanocrystalline of B4C and amorphous of Ti. TEM showed typical nanocomposite structure which the nanocrystalline B4C phase is embedded in Ti amorphous phase. The maximum hardness of42GPa occurred at the deposition temperature of400℃and work pressure of0.5Pa. The hardest coating also showed the lowest residual stress and the highest critical load. Meanwhile, the lowest friction coefficient occurred at room temperature.Nanocomposite nc-B4C/a-Si3N4coatings were prepared using magnetron sputtering at different substrate bias and substrate temperature from Si3N4target and B4C target respectively by multi-target magnetron co-sputtering. The relationship beween the microstructure, mechanical properties, tribological performances and deposition temperature and substrate bias were investigated. The B4C(104), BNX(311) peaks appear in XRD patterns. TEM showed typical nanocomposite structure which the nanocrystalline B4C phase is embedded in Si3N4amorphous phase. The strong sp3-BN peak appears in the XPS spectra when bias is-100V, revealing higher fraction of sp3-BN, this would affect mechanical property enhance. The maximum hardness of34GPa and elastic modulus of394GPa were achieved at optimal deposition parameters including a pulsed substrate bias of-100V, and a substrate temperature at400℃. Meanwhile, the coating also showed highest critical load of188mN and lowest friction coefficient of0.12. In addition, nanocomposite nc-B4C/a-Si3N4coatings were able to keep higher hardness after annealing.All results above demonstrated that nc-B4C/a-Ti and nc-B4C/a-Si3N4nanocomposite coatings with high hardness, fractuer resistance, and low friction coefficient can be synthetized by multi-target co-sputtering system with optimized parameters during deposition. Therefore, these coatings have great potential as protective coatings on cutting tools and other mechanical components.