关键词: 激光熔覆, 裂纹, 耐摩擦性, 镍基合金, 钽, 碳化钽

Abstract: Influence of Ta element on microstructure, crack susceptibility, microhardness and abrasive wear resistance of laser clad Ni60 coating are investigated. SEM shows that crack tends to initiate and propagate downwards along grain boundary of coarse hard phase, which is typical characteristic of hot crack. After the addition of Ta into the coating, TaC particle first grows up in melting pool, which suppresses growth of primary M7C3. With an increase of Ta content, the amount and length of cracks on the surface of the coating obviously decrease, which is attributed to refining of M7C3 and increasing of the coating’s toughness. Although the microhardness decreases due to the addition of Ta, abrasive wear test shows abrasive wear resistance of Ni60+Ta coating largely increases compared to pure Ni60 coating. The reasons are shown as follows: the supporting ability of γ-Ni matrix to support hard phase is improved due to Ta solid-solution strengthening; the fragileness of the primary M7C3 carbide decreases with it’s aspect ratio; additionally, in situ synthesized fine TaC particles are hardly pulled out from the wear surface, which is beneficial to protect the matrix from being cut.

Key words: Cracks, Laser cladding, Nickel alloys, Tantalum, Tantalum carbide, Wear resistance