摘要
Ternary Ni-P-W and Ni-P-Cr alloy molding coatings were fabricated by radiofrequency (RF) magnetron sputtering onto steel substrate, AISI 420 tool steel. Cycling annealing up to 500 °C was performed on various Ni-P-based coatings to simulate the cycling injection or press-molding process in practical use. The mechanical properties, including hardness and Young's modulus of the alloy coatings, were evaluated by continuous stiffness measurement. It was observed that the ternary Ni-P-Cr and Ni-P-W coatings exhibited a maximum hardness up to 14 and 15.5 GPa under 8 and 12 h of annealing test at 500 °C, respectively. With long-term annealing up to 20 h at elevated temperature, the Ni-P-based coatings retained a steady hardness of 12 GPa. The influence of the third element introduction on the mechanical properties of the Ni-P-based coating was probed and discussed. The incorporation of W and Cr into the NiP-based coating exhibited superior mechanical behavior under elevated temperature environments as compared to Ni-P binary coating. In addition, the correlation between indentation penetration depth and mechanical behavior was also evaluated. Reliable hardness values of the coatings were extracted from the indentation range of 200-400 nm, while the gradual descent in hardness with increasing indentation depth was influenced by the substrate effect. © 2004 Elsevier B.V. All rights reserved.