Fracture Strength of PIRAC Titanium Nitride Coatings Evaluated by Bending Methods

The fracture strength of titanium nitride coatings prepared on Ti6Al4V by powder immersion reaction-assisted coating (PIRAC) at 700 degrees C for different processing times has been studied. First, the fracture strength estimation expression was developed based on experimental bending phenomena and deformation analysis, as well as by considering the difference of the mechanical properties of the substrate and titanium nitride coating. The results showed that the fracture strength of the prepared PIRAC titanium nitride coatings increased with increasing processing times. The fracture strengths of the PIRAC titanium nitride coatings prepared at 700 degrees C for 24 h, 48 h, 96 h, and 144 h were about 492.3 MPa, 546.6 MPa, 576.5 MPa, and 729.3 MPa, respectively. Further analysis indicated that such increments of the fracture strength of the coating resulted from the variation in composition, especially, the contents of TiN and Ti2N with higher mechanical properties increased with increasing processing time.