Process Study Of Ni60-WC Composite Coating On 17-4PH Stainless Steel By Induction Cladding

In this paper, WC-Ni60 composite coatings were prepared on the surface of cylindrical samples and square samples of 17-4PH stainless steel by high velocity oxygen fuel-induction cladding respectively. Moreover, the effects of structural state, defects, dense degree, bonding quality with matrix, phase composition, surface roughness and hardness of the coating layer with different cladding current, preheating current, moving speed, particle state of cladding materials were investigated.The results showed that, with the increasing of the cladding current, layered structure of coating disappeared, pores of coating were reduced, and structures were dense gradually. Interface bonding between the coating and the matrix increased gradually, from half machine-half metallurgical bonding with spraying into a metallurgical bonding. The surface roughness value and the surface hardness of cladding layer on cylindrical samples had a decreasing trend with the increasing of the cladding current; the surface roughness value of cladding layer on square samples increased first and then decreased, and the surface hardness decreased. The research on different moving speeds of cladding samples indicated that, with small moving speed, layered structure of coating disappeared, pores of coating were reduced, and structures were dense. The interface bonding became a metallurgical bonding. The surface roughness value and surface hardness were small with small moving speed. The research on the original powder coating materials with different particle size showed that, the finer the powder size was, the more uniform and denser the structure was, and the smaller the surface roughness value was. Preheating had some influence on the induction cladding. The better result was obtained with immediately remelting cladding after preheating, the coating was more uniform and denser, and the surface roughness value was small. The study also showed that, the phases of coating after induction cladding were as same as the phase of powder before cladding. Whether cladding or not, the phases of coating materials had not changed, it was mainly consisted of y-Ni, WC, FeNis,Cr23C6, Cr3C2, FexNi23-xB6, Ni3Si and Cr7C3. The intensity of diffraction peak varied, indicated that the relative content of precipitation phase changed. The microhardness of the coating layer was higher than 17-4PH stainless steel substrate significantly; it was almost 3 to 5 times higher than the microhardness of substrate approximately. Induction cladding had a small heat affected zone on matrix.The influences of cladding current, preheating current, moving speed, particle size and other parameters provided a reliable experimental basis to the best preparation process of Ni60-WC composite coating, further proved that induction cladding was an effective way on densification of Ni60-WC composite coating.