International OPEN ACCESS Journal Of Modern Engineering Research (IJMER) | IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 5 | Iss.2| Feb. 2015 | 11| Effect of Molybdenum Disulphide on Physical Properties of Neodymium-Iron-Boron Bonded Magnet Lijesh K.P. 1 , Harish Hirani 2 , Samanta P. 3 1 (Mechanical Department, Indian Institute Technology Delhi, India 2 (Mechanical Department, Indian Institute Technology Delhi, India 3 (Surface Engineering and Tribology, CMERI Durgapur, India I. INTRODUCTION Bearings can be classified into three categories: (i) Rolling bearing, (ii) Fluid film bearing and (iii) Magnetic bearing. The rolling bearings are known for their efficient performance particularly at high load and low speed conditions. The major disadvantages of such bearings are: (i) Inability to handle misalignment [1, 2], (ii) Requirement of regular maintenance and (iii) Performance sensitivity towards dusty environment. Fluid film bearing provides low friction and wear [3] by limiting the metal to metal contact. A well designed fluid film bearing can tolerate some misalignment, fluctuation in speed/load/moisture and unexpected dirt. Such bearings provide high damping [4, 5] due to liquid lubricants. However on increasing load and/or reducing the relative speed decreases the thickness of fluid film and increases the chances of bearing wear. In other words, the performance of fluid film bearing decreases drastically at “low speed [6] and high load [7,8]” conditions. Magnetic bearings provide frictionless and zero wear operations, due to which their applications in industries is increasing. Magnetic bearings can be classified into (i) Active magnetic bearing and (ii) Passive magnetic bearing. Active magnetic bearings [9, 10] support the rotor using magnetic flux produced by current carrying wire wound around the stator core and provide complete separation between rotor and bearing metals. A major drawback of these AMBs is the essential requirement of closed feedback control system to locate the position of rotor ([11]), which means high initial as well as running costs [8, 12] of these bearings. High running cost is due to: high bias current, hysteresis, eddy-current particularly at high speed and windage losses. In addition AMBs require supplementary set of bearings (i.e. rolling element bearings) to support the rotor when AMB fails, so that the rotor does not hit the AMB surface and damage the working of whole system. Alternatively a lesser costly magnetic bearing [13,14], termed as “passive magnetic bearing” as it does not require any control system, which relies on the repulsion between two permanent magnets (stator and rotor) to levitate the rotor from stator can be employed as frictionless bearings. Low load carrying capacity [15], is one of the drawback of permanent magnet bearings, which can be enhanced by using high power rare earth magnets. However, the neodymium magnetic materials are highly brittle [16, 17] and are highly porous in nature. Porosity of magnet inherently comes from powder metallurgy processes [18]. These porosities aggravate the strength of the magnets and restrict their usage in magneto-hydrodynamic bearings [14-16], high rpm and low clearance electric motors, and structural elements. Any improvident use of the magnets in such precarious conditions may cause the breakage of magnets. Therefore, it is important to enhance the mechanical strength of magnets. Improvements in bending, fracture, and uniaxial tensile strengths of NdFeB using sintering process, have been reported [19]. Rowlinson et al [20] reported the enhancement of fracture strength of bonded magnets made by rotary-forging using melt-spun ribbon material. They tried mixing of soft metal such as Al, Zn, Sn, and Cu. They concluded Al-bonded magnet exhibit high mechanical strength. But that mechanical improvement had been achieved at the loss of magnetic properties. Garell et al [21] studied the mechanical properties of PPS bonded and Nylon bonded magnets. They could increase the ultimate strength by decreasing ABSTRACT: The present paper reports the effect of molybdenum disulfide (MoS 2 ) on magnetic and mechanical properties of neodymium iron boron (NdFeB) bonded magnet. Powder metallurgy process has been used to prepare the test samples containing 0.0, 0.5, 1, 1.5 and 2 percentage of MoS 2 . Compact and hardness tests have been performed to measure the physical properties of samples. Saturation magnetization, remanence and intrinsic coercivity have been checked using vibrating sample measurement (VSM) test Keywords: Neodymium iron boron, Molybdenum disulfide, Magnetic Property, Mechanical property