Fabrication of Crystalline Ni-B-Al2O3 Composite Coating by Electroless Method and its Tribological Characterizations

Subject Areas : journal of New Materials

H. KH ¹ (دانشجوی کارشناسی ارشد، دانشگاه آزاد اسلامی، واحد نجف آباد، دانشکده مهندسی مواد، نجف آباد، ایران)
A. I.N.P ² (استادیار، دانشگاه شهید باهنر کرمان، دانشکده فنی و مهندسی، کرمان، ایران)
S.A حسن زاده تبریزی ³ (استادیار، دانشگاه آزاد اسلامی، واحد نجف آباد، دانشکده مهندسی مواد، نجف آباد، ایران)

Received: 2014-07-01 Accepted : 2014-07-01 Published : 2014-08-23

Keywords: electroless Ni-B, Al2O3, Heat-treatment, hardness, wear resistance,

Abstract :

In the current investigation a Ni-B-Al₂O₃composite coating was fabricated through electroless method and the effects of heat treatment on microstructure, hardness and tribological properties was studied. Electroless Ni-B-Al₂O₃ coating of 30 µm thickness was applied on the surface of Ck45 steel. Following that, the coated samples went through heat treatment for 1 h at 400 ˚C. X-ray diffraction and scanning electron microscopy were utilized in order to characterize the coating. Tribological behavior and hardness of the samples were studied by means of pin on disk and Vickers microhardness measurement device.  The results revealed that the addition of Al₂O₃ particles leads to grain refinement and consequent microhardness elevation. Moreover, heat treatment resulted in nanocrystalline structure, therefore, hardness and wear resistance of the coating improved due to transformation of  amorphous phase to crystalline structure and production of Ni₃B phase.