Heat Treatment Effect on Properties of Ni-P-Al 2 O 3 Composite Coatings

  • PDF / 793,670 Bytes
  • 6 Pages / 432 x 648 pts Page_size
  • 62 Downloads / 233 Views

DOWNLOAD

REPORT


Mater. Res. Soc. Symp. Proc. Vol. 1243 © 2010 Materials Research Society

Heat Treatment Effect on Properties of Ni-P-Al2O3 Composite Coatings Carlos A. León-Patiño, Josefina García-Guerra, Ena A. Aguilar-Reyes, José Lemus-Ruiz Instituto de Investigaciones Metalúrgicas, Universidad Michoacana de San Nicolás de Hidalgo, A.P. 888 Centro, C.P. 58000, Morelia, Mexico ABSTRACT Ni-P and Ni-P-Al2O3 composite coatings are obtained by electroless plating on steel substrates. Alumina particles with an average particle size of 5 microns are added to the bath in loads of 5, 10, 15 and 20g/L. It is found a maximum retention of 18.2 vol.% Al2O3 for a ceramic load of 10g/L. The composition of the binary Ni-P deposits is 9.3 wt.% P and the balance nickel. The addition of ceramics to the electroless solution induces a reduction of phosphorous content to 9.0, 8.3, 7.9 and 7.3%, respectively. The deposited coatings are heat-treated in the temperature range between 100 and 500ºC and holding times from 30 to 300 minutes. A maximum hardness of 1600 HV0.1 is obtained for composite coatings containing 18.2 vol.% Al2O3 treated at 400 ºC/1h. The uniform distribution of ceramics and precipitation of fine Ni3P and Ni12P5 precipitates are responsible of the hardening of the nickel matrix. INTRODUCTION Electroless Ni-P deposits have been the subject of various investigations owing to their excellent properties, including hardness, wear resistance, corrosion resistance and magnetic characteristics. Since these properties depend primarily upon the structure and phosphorus content of the deposits, many studies have been carried out to characterize the as-deposited structure as a function of phosphorus content [1,2]. Notwithstanding the several applications of Ni-P deposits, their properties can be further enhanced by co-deposition of hard or lubricant particles such as SiC, Al2O3, B4C and PTFE [3-7]. One of the main purposes of the ternary deposits is to improve the wear behavior of material surfaces; therefore, the fraction and nature of reinforcing particles, and composition and thermal history of the matrix are of important consideration. These deposits have a high hardness, particularly after heat treatment above 250°C [8]. Among the reinforcing ceramics, Al2O3 is extensively used due to its high hardness, elastic modulus, wear and good oxidation resistance. Despite several investigations, there is a little information on the effect of alumina content on the heat treatment response of Ni-P matrices, and its relationship with the phase evolution and hardness properties of Ni-P-Al2O3 composite coatings. In the present study, the microstructure and hardness properties of electroless Ni-PAl2O3 with different amounts of reinforcing alumina is investigated after heat treatment in the temperature range 100-500°C. EXPERIMENTAL DETAILS Electroless Ni-P and Ni-P-Al2O3 coatings are applied on the surface of O1 tool steel substrates with dimensions 2x2x0.3 cm. The substrates are surface finished with silicon carbide abrasive paper to grade 600; then clean

Data Loading...