Surface treatment of a metal part by oblique shot peening

Abstract

A process for the surface treatment of a metal part comprises exposing a surface of the metal part to a stream of substantially spherical particles, so that any portion of said surface receives said particles along several primary incidences, the primary incidences of the particles on a portion of the surface being essentially distributed in a cone or a conical film which has an outer half apex angle between 10° and 45°, until a surface layer of nanostructures having in particular an average thickness of greater than 50 μm is obtained, the particles having a diameter of less than 2 mm and greater than 0.1 mm and being projected at a speed between 40 m/s and 100 m/s.

1 . A process for the surface treatment of a metal part, comprising:
 exposing a surface of the metal part to a stream of particles having a sphericity greater than or equal to 85%, so that said surface receives said particles along several primary incidences, the primary incidences of the particles on the surface being distributed in a cone or a conical film which has an outer half apex angle (α, α+β, α−β) between 10° and 45°, until a surface layer of nanostructures is obtained, the particles having a diameter of less than 2 mm and greater than 0.1 mm and being projected at a speed between 40 m/s and 100 m/s,   wherein the stream of particles comprises a jet of particles projected by projection means along a central direction, the metal part being fixed to a support so that the inclination (α) of the surface of the part exposed to the stream with respect to the central direction is between 10° and 30°, the support or the projection means being rotated about an axis coaxial with the central direction of the jet of particles.   
     
     
         2 - 3 . (canceled) 
     
     
         4 . The process according to  claim 1 , wherein the particles have a diameter of greater than 0.3 mm and of less than 1.4 mm. 
     
     
         5 . The process according to  claim 1 , wherein the incidences of the particles are distributed substantially continuously. 
     
     
         6 . The process according to  claim 1 , wherein the cone or the conical film has an outer half apex angle of between 10° and 30°. 
     
     
         7 . (canceled) 
     
     
         8 . The process according to  claim 1 , wherein the inclination (α) of the surface of the part exposed to the stream with respect to the central direction is 15°. 
     
     
         9 . The process according to  claim 1 , wherein the particles are projected at a speed of between 50 and 80 m/s. 
     
     
         10 . The process according to  claim 1 , wherein the particles have a hardness greater than the hardness of the surface of the part before treatment. 
     
     
         11 - 13 . (canceled) 
     
     
         14 . A surface treatment device for a metal part, comprising:
 a projection means capable of producing a stream of particles having a sphericity greater than or equal to 85% and having a diameter of less than 2 mm and greater than 0.1 mm and that are projected at a speed of between 40 m/s and 100 m/s, the projection means being capable of producing a jet of particles projected along a central direction;   a support capable of holding a metal part, the support comprising a surface exposed to the stream of particles; and   an actuator capable of modifying an orientation of the support with respect to the stream of particles so that the primary incidences of the particles on a surface of the support are distributed in a cone or a conical film that has an outer half apex angle of between 10° and 45°, the surface of the support being oriented obliquely with respect to said central direction, the actuator being capable of pivoting the support about an axis that is coaxial with the central direction of the jet of particles.   
     
     
         15 . (canceled) 
     
     
         16 . The process according to  claim 1 , wherein the jet of particles has a conical-shape which has an outer half apex angle (β) lower than the inclination (α) of the surface so that the primary incidences of the particles on the surface are distributed in a conical film. 
     
     
         17 . The surface treatment device according to  claim 14 , wherein the particles have a diameter of greater than 0.3 mm and of less than 1.4 mm. 
     
     
         18 . The surface treatment device according to  claim 14 , wherein the particles are projected at a speed of between 50 and 80 m/s. 
     
     
         19 . The surface treatment device according to  claim 14 , wherein the particles have a hardness greater than the hardness of the surface of the part before treatment. 
     
     
         20 . The surface treatment device according to  claim 14 , wherein the primary incidences of the particles are distributed substantially continuously.