Laser boronizing of copper alloy

Surface hardening of Cu-Ni alloy has been successfully achieved by laser alloying with boron powder. Powder was preplaced in a groove on the plate surface of the base metal, and irradiated by a defocused CO sub 2 laser beam with 2.5-3.5 kW at a travel speed of 100 mm/min under Ar shielding. The structure of the alloyed layer consisted of very hard boron particles, hard Ni boride (mainly NiB) and a soft Cu-Ni solid solution phase. With an increase of Ni content, the volume fraction of boride increased but that of boron particles decreased. Hardness of the alloyed layer increased to Hv 400-500 up to 30 mass% Ni and increased monotonicaly with the increase of Ni content and reached Hv 1400 at pure Ni plate, which corresponded to the hardness of Ni boride. Wear resistance of the alloyed layer improved to 40 times that of base metal for each Cu-Ni alloy.