Thermal stability of sputtered Ni–P and Ni–P–Cr coatings during cycling test and annealing treatment

Binary Ni–P and ternary Ni–P–Cr alloy coatings were fabricated by the RF magnetron sputtering technique with dual targets of electroless nickel alloy and a third element metal. The compositions of the as-deposited alloy were measured by electron probe microanalysis. The phase identification was carried out by X-ray diffraction technique. The as-deposited Ni–P and Ni–P–Cr coating exhibited amorphous structure. The thermal property of coating was investigated by the annealing test for 4 h and by the cycling test for 30 min in N2 atmosphere at 400 and 450 °C. The related mechanical properties were evaluated by Knoop microhardness test, and measured microhardness was employed to evaluate the thermal stability of the binary and ternary alloy. The microhardnesses were 1250 and 1380 HK for both the Ni–P alloys at 400 °C and ternary Ni–P–Cr at 450 °C, respectively, after 4-h annealing. For cycling test over 8 times cycles at 400 °C, the microhardness of Ni–P–Cr deposit was 1200 HK, in which full phase of Ni3P precipitation was not completed. The influence of adding element Cr on the thermal properties of Ni–P-based alloy coating was also discussed.