Brazing method for improving connecting strength of PDC and steel matrix

The invention discloses a brazing method for improving the connecting strength of PDC and a steel matrix. The brazing method comprises the following steps that the drill bit steel matrix and a PDC hard alloy section are pretreated; the pre-treated PDC hard alloy section is subjected to laser etching treatment, then cobalt plating and nickel plating are carried out on the PDC hard alloy section insequence, so that the PDC hard alloy sections form a cobalt-nickel composite coating; a tooth hole is machined in the drill bit steel matrix, and the circumferential surface of the tooth hole is subjected to wire drawing treatment and then washed with acetone; the circumferential surface of the PDC hard alloy section coated with the cobalt-nickel composite coating and the circumferential surface of the tooth hole after wire drawing treatment are coated with elemental boron and nickel-cerium alloy mixed powder; after a brazing filler is placed on the bottom of the tooth hole coated with the elemental boron and the nick