Coating properties of Ni and Ni alloys deposited by wire explosion spraying method

摘要

Nickel, nickel-chromium and inconel coatings were deposited on mild steel substrates by the explosion spraying method with various energy densities. The effects of spraying conditions on the microstructures, constitution and mechanical properties (hardness and adhesive strength) of their coatings were investigated. (1)The numbers of pores decreased in the Ni and Ni-Cr coatings obtained at the energy density range over 55kJ/cm{sup}3, which resulted in higher densification. However, clearances were observed between the grains in inconel coatings sprayed at the energy density range over 50kJ/cm{sup}3. (2)Ni, NiCr and Ni-Cr-Fe solid solution were detected by X-ray diffraction analysis for the nickel, nickel-chromium and inconel coatings respectively formed by explosions of 5 times. NiO were found in all coatings. The constitution of inconel coatings slightly changed from that of the original inconel wire. (3)Both hardness and adhesion strength of all the coatings increased with a certain increase of energy density and reached to the maximum values, After reaching to the maximum values, however, these properties lowered with increasing the energy density. (4)Wire explosion spraying method operated under adequate conditions, such as energy density rages over 55kJ/cm{sup}3 for the Ni and Ni-Cr coatings or nerar 40kJ/cm{sup}3 for the inconel coating, makes it possible to form relatively dense coatings with smooth surface and to obtain the coatings hardness of 200～250HV higher than that of each original wires.