Investigation of Machining of Stellite 6 Alloy Deposited on Steel Substrate

The present paper brings an insight to face the machining of hard coatings (Stellite 6) prepared by thermal spraying technology. The objective of the paper is to evaluate the influences of machining parameters on the surface of Stellite 6 deposited on steel substrate by the high-velocity oxygen-fuel (HVOF) thermal spray process. Stellite 6 belongs to the most widely used cobalt-based alloys. Its exceptional wear resistance is mainly due to the unique properties of the hard carbide phases dispersed in the CoCr matrix. The efforts to achieve the maximum economic effect of mechanical machining of applied coatings lead to the verification of the possibilities of machining of these coatings by turning. Cylindrical specimens of 54.7 mm in diameter from the C45 base material were coated with Stellite 6 with an average value of 0.55 mm. From experimental results in the range of cutting rates from 150 to 250 m·min−1, feed rates from 0.4 to 1.0 mm· rev−1 and cutting depths of 0.1 and 0.15 mm, the predictive models of roughness parameters Ra and Rz were compiled using mathematical and statistical methods followed by subsequent application of neural networks in order to confirm the obtained conclusions. At present, turning can be used only for machining of the coatings applied by thermal spraying having relatively good plastic properties and relatively low hardness. Research results have proved that feed turning technology is a suitable technology for machining coatings generated by Stellite 6 alloy thermal sprays in such user cases where additional surface treatment is required for specific reasons.