Bond strength of an Fe-Al-based coating as influenced by cutting parameters and the dynamic characteristics of a compound NC machine tool

摘要

Arc spraying of Fe-Al-based coatings is widely used in for remanufacturing and other requirements due to its high performance; however, the bond strength between coating and substrate is about 50 MPa, so the changes therein are important in the cutting process. Moreover, such coatings are thin, and their surface is coarse, so this predefines two cutting steps in any subsequent machining process. It indicates that three factors affect the bond strength including the following: machine tool natural vibration, cutting tool regenerative vibration, and forced vibration due to the rough surface. This work presents a spindle-tool-workpiece vibration model of the coating machining process and studies the effects of transient cutting force, residual stress, and cutting parameters on the bond strength. The results show that the transient maximum influence of cutting force on the bond strength is 7.27 MPa, and the residual stress affects the material to a depth of 1.6 mm. Then, a bond strength calculation model was obtained to calculate the bond strength reduction as induced by choice of cutting parameters. The calculation model was verified experimentally, and it was shown that cutting depth was the main factor affecting bond strength. Combined with SEM inspection, this work showed that the interface gap was amplified during cutting. Importantly, to achieve the necessary bond strength, the first cutting depth should be less than 0.1 mm (allowing for the surface dimensional difference), and the cutting depth of other cutting steps should be less than 0.2 mm; in addition, the finishing coating thickness should be more than 0.2 mm.