Method and device of enhancing diffusibility of metallic surfaces and applications thereof

Abstract

A method for increasing diffusibility of metallic surfaces and its applications in surface treatment of metallic implants, which combines a mechanic means and a chemical means, whereby the mechanic means increases the diffusibility of the surface while the chemical means forms a chemically modified surface layer for improved properties suitable for particular application of the metallic materials, especially in the bio-medical areas. This surface treatment can increase the hardness and corrosion resistance of stainless steel and reduces Ni release from implants made from NiTi wires.

1 . A method of enhancing diffusibility of a metallic surface, comprising a step of generating crystalline surface structure by surface mechanical attrition treatment. 
     
     
         2 . A device for generating nanostructures in a given thickness on metallic implants comprises a working chamber that can be divided into multiple rooms, means for setting in motion a given quantity of perfectly spherical balls of given dimension at a given speed in each room for a given duration, means for reusing the balls continuously in each room, and means for mounting and rotating the implants at a given speed to obtain variable angles of incidence at the same impact point, so that the impact points as a group cover the entire surface of the implant. 
     
     
         3 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 2 , further comprises fences to separate the rooms of the working chamber. 
     
     
         4 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 3 , at least one room has adjustable roof height. 
     
     
         5 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 4 , further comprises an ultrasonic generator at the bottom of each room to set the balls in motion, causing the balls to move in random directions. 
     
     
         6 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 4 , further comprises the sloping floor of each room to reuse the balls. 
     
     
         7 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 6 , in which the implants are intramedullary nails, bone plates, artificial hip joints, etc made of stainless steel, and NiTi wires. 
     
     
         8 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 6 , further comprises clamps or other fixtures to fix the implants, which are mounted in the tubes driven by a motor through gears at a rotation speed between 0.5 rpm and 5 rpm. 
     
     
         9 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 6 , further comprises fixtures to move NiTi wires in a linear speed between 10 cm/min and 40 cm/min. 
     
     
         10 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 6 , in which the perfectly spherical balls are made of stainless steel or zirconia with diameter, depending on the thickness of the nanostructures desired by the user, being 0.3 mm to 3 mm. 
     
     
         11 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 6 , in which the balls are of a quantity such that, when the means for setting them in motion using ultrasound are inactive, they occupy a surface area greater than 30% of the surface of the sonotrode. 
     
     
         12 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 6 , in which the ball speed is between 5 mps and 100 mps. 
     
     
         13 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 6 , in which the projection time, determined based on the nanostructured layer thickness desired by the user for a given ball size and a given material constituting the implant with given size, is between 30 s and 1800 s. 
     
     
         14 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 13 , further comprises means for adjusting the emission time of the balls. 
     
     
         15 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 6 , in which the distance between the emission source of the balls and the implant being treated is between 20 mm and 80 mm. 
     
     
         16 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 15 , further comprises means for adjusting the distance. 
     
     
         17 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 6 , further comprises means for performing a local cooling of the treated area of the implant. 
     
     
         18 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 6 , in which the projection step is performed after the chamber has been filled with inert gas. 
     
     
         19 . The device for generating nanostructures in a given thickness on metallic implants according to  claim 5 , which is enclosed in a vacuum cabinet.