Microstructure and Microhardness of Tempered Ni-Al Alloyed Layer

A Nd: YAG pulsed laser was used to alloy the Ni-P electroless deposited coating with aluminum substrate under the condition of scanning speed of 3.0 mm/s and power density of 5.36 × 109 W/m2. Subsequently, the samples were heat treated at 300, 400 and 500 °C for 2.5 h, respectively. The phase composition and microstructure of the tempered layers treated at different temperature were identified by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the phase constituents of the alloyed zones were intermetallic compounds of NiAl, Al3Ni, Ni3P and AlNi3. As a result, the microhardness of the alloyed layer after heat treatment was improved obviously compared to untreated samples, and the layer obtained at temperature 400 °C reached HV0.1 430.