**2.1. Grit blasting and TiN film prepared**

AISI 440c stainless steel was chosen as substrate for sand blasting and TiN film prepared. Before grit blasting, the stainless steel substrate was grinded with emery papers and rinsed with acetone and ethanol to get rid of impurity. Grit blasting was carried by a handheld sand blasting machine (China, JICHAN TECH) using 60# Al<sup>2</sup> O3 particles (diamond 300 μm, JICHAN TECH). After then, the morphology of steel substrate was characterized by a JSM-5600LV scanning electron microscope, which attaches with energy disperse spectrometer.

The hard titanium nitride film was prepared using ion plated technology with Hauzer Flexicoat 1200 coating. The deposition parameters were following: 60 A of arc current, 200 V of bias volt, 400 centigrade degree of steel disks, 100 min of deposition time, and 1.8 Pa of N<sup>2</sup> pressure.
