Steel bearings can be coated with sufficient adhesion power by means of a low temperature PVD process below 160 C. Titanium derivative coatings bring advantages in avoiding tribological trouble in high stress conditions.
The fatigue properties of coatings were determined through the impact test and its FEM simulation. The derived fatigue critical stress values were successfully applied in the evaluation stage of the experimental results of the ball on rod RCF test, permitting herewith their further application in full scale bearings.
The results of the bearing simulation predicted the adequacy of coatings to operate in prescribed conditions without fatigue failure. The experimental results during the long term bearings evaluation confirmed the predicted behaviour.
As a result of the increasing use of high-speed high-performance cutting on the grounds of economic efficiency, angular contact ball bearings which attain a speed characteristic of n*dm = 2 to 2,5*106 mm/min at a bore diameter on a scale of 50 to 100 mm are required. Due to friction and wear, hower, angular contact ball bearings possess a maximum speed characteristic of approx. 1.75*106mm/min, i.e. they do not attain the required performance values. When minimum friction lubrication is employed, this limit is given by the contact conditions within the bearing and the wear on the surfaces of the rolling partners. The level of wear is dependent on the affinity existing between the respective rolling partner materials. The degree of affinity can be substantially reduced by changing the material pairings employed.
The aim of this project is to increase the performance of main spindles using newly developed angular contact ball bearings with ceramic balls and coated steel races. Furthermore it is intended to adapt the design characteristics for the spindle bearing system to the changed tribological and mechanical characteristics of these bearings. Coating of the individual components is to be carried out by means of the PVD process. It is intended to apply single and composite coatings.
Funding SchemeCSC - Cost-sharing contracts
40069 Zola Predosa Bologna