Fig. 1. Comparison of morphology (a, d), Raman spectroscopy (b, e), hardness and elastic modulus (c) of NBG-18 before and after deposition of PLC coating, (f) film-based adhesion of NBG-18 deposited with PLC coating

Fig. 2. Friction coefficients of NBG-18 with PLC coating deposited in a nitrogen environment at room temperature under different loads (a), frequencies (b), and different conditions (c)

Fig. 3. White light interference morphologies of worn NBG-18 (a~d) and steel balls (e~h) deposited with PLC coatings under different loads (a, e) 1 N, (b, f) 2 N, (c, g) 5 N, (d, h) 10 N

Fig. 4. Raman spectra of NBG-18 friction region of PLC coating deposited under different loads (a⁓e), and the I_D/I_G value of NBG-18 friction zone with PLC coating deposited under different loads (f) (color online)

Fig. 5. White light interference morphology of NBG-18 graphite blocks (a, b) and corresponding PLC balls (c, d) before and after deposition of the PLC coating under a normal load of 2 N and a sliding frequency of 5 Hz (color online)

Fig. 6. NBG-18 abrasion marks and friction ball spots deposited on PLC coating under normal load of 2 N and sliding frequency of 5 Hz: (a) Super depth morphology of NBG-18 abrasion marks deposited on PLC coating; (b) Central Raman spectroscopy of abrasions; (c, d) Raman spectra of the left and right edges of the abrasion marks; (e) Spherical spot ultra depth of field morphology; (f) Raman spectroscopy of the non worn area of the friction ball; (g) Raman spectroscopy at the center of the spherical spot; (h) Raman spectroscopy at the edge of the spherical spot (color online)