Method and apparatus for depositing raised features at select locations on a substrate to produce a slip-resistant surface

A method for producing a slip-resistant surface on a substrate having a generally planar surface comprising the steps of:

• a) providing a metallic substrate having a generally planar surface;
• b) providing a radiant energy source selectively positionable adjacent to the surface, the energy source emitting a high energy beam and having a focusing device for varying the focal length of the beam, and a control device for managing the beam, the energy beam having an axis and a focal point, the axis aligned to intersect with the surface at an angle and the focal point being generally on the surface at a beam impingement point;
• c) providing a powder supply apparatus having a supply of powder particles, and a powder feed tube with generally opposing first and second ends, the first end connected to the supply, the second end being open and generally directed toward the beam impingement point, the powder feed tube being disposed to convey the powder particles from the supply and discharge the particles generally toward the beam impingement point;
• d) supplying, via the powder supply apparatus, substantially simultaneously with projection of the energy beam, a predetermined flow rate of powder particles generally toward the beam impingement point on the substrate;
• e) intermittently projecting for a pre-selected duration and frequency, an energy beam from the radiant energy source generally toward the surface to the impingement point, the focal length of the energy beam coinciding with the separation between the energy source and the impingement point;
• f) allowing partial melting of the substrate surface material proximate to the impingement point and of the powder particles to form an alloy of the two proximate to the impingement point, the partial melting of the substrate creating a fusion zone extending above and below the surface of the substrate, the fusion zone having a depth below the surface of the substrate;
• and
• g) allowing additional powder particles to be melted and form a feature extending from the substrate surface and having a height approximately twice that of the fusion zone extending below the surface of the substrate.