Study On Physical And Chemical Properties Of NaCl-type Fcc-TiBCN Powder

With the increasing demand for super-hard materials, compound of the Ti-B-C-Nsystem, such as quaternary TiBCN, ternary TiBN and TiBC, are becoming more andmore attractive because of their excellent mechanical and tribological propertieswhich are proved by many literatures, even though the relevant research of thesematerials just focus on the thin film. These thin films are usually synthesized by PVD(Physical Vapor Deposition) or CVD (Chemical Vapor Deposition) methods. Intenseresearch, application and popularization of TiBCN material are limited due to thecomplex processing, high cost and low efficiency of the deposition of thin film.The Fcc-TiBCN powder extends the applications in many fields as corrosion andwear resistance coating materials, functionally graded materials, metastablemulti-function composite materials, electrode materials and target materials, followedby its successful production. Furthermore, it can create new research projects andsimplify the manufacturing process of various films. Also the cost of production canbe reduced. It can make the application of super-hard、wear and corrosion resistancematerials containing TiBCN develop very fast. The results on the physical andchemical properties of Fcc-TiBCN powder provide theoretical and scientific guidancefor making process of production in large scale, purifying of powder, applications andmarketing.In this study, the main component, trace and impurity element of the Fcc-TiBCNpowder were analyzed qualitatively and quantitatively by utilizing the modernanalysis and measurement technologies, such as XPS, XRD, SEM, TEM, etc. Bindingenergy and chemical state of the main element, phase component and crystal structure,the second phase and the crystal relationship to the matrix were studied. The TiBCNsintered parts were prepared. The microstructure and properties were studied and the sinterability and machinability of the Fcc-TiBCN powder was evaluated. Meanwhile,cladding layers were prepared on TC4titanium alloy and45steel by using TIG andlaser cladding processing. The microstructure and microhardness were studied. Theapplicability and feasibility of TIG and laser cladding with the Fcc-TiBCN powderwere evaluated.The major results of the present study are as fellows:(1) It has been demonstrated that the TiBCN powder exhibits a NaCl-typeface-centered cubic structure as confirmed by XRD analysis. The synthesistemperature affects lattice parameter and phase component of powder. Latticeparameter of which is large and unstable at low synthesis temperature. Withtemperature gradually increasing, the lattice parameter of Fcc-TiBCN powder tendedto be stabilized to4.241in the range of770～870℃; Stabilityat elevated temperature of Fcc-TiBCN powder exhibited as the grain size did not growup. The purity of Fcc-TiBCN powder increased when some product disappeared atlow temperature. The second phase TiB2, Ti5Si3, TiF3and NaF are dominant. Thecrystal defects are characterized dislocations and twins with (111) twin plane.(2) Main component element of Fcc-TiBCN powder are Ti, B, C and N，impurityelement are O, Na, Si and F, etc. The atom percentage of Ti, B, C and N are40～43.35%,8.77～9.51%,4.88～5.29%and38.60～41.85%, respectively.Non-stoichiometric molecular formula of Fcc-TiBCN powder can be defined asTi43.3B9.5C5.2N42, belonged to supersaturation solid solution.(3) Main element energy levels of Ti2p3/2, Ti2p1/2, B1s, C1s, N1s and O1s inFcc-TiBCN powder are457.5eV,463.4eV,190.9eV,284.7eV,397.4eV and535.5eV,respectively. The binding energy shift of every element is larger than3eV comparingto the standard value. More than one bonding state existed with surrounding Ti, B, Cand N, the principal chemical bonds are Ti-N, Ti-B, Ti-C, B-N, B-C, C-N, and Ti, B,C or N bonds with O, such as Ti-O and B-O. It was shown that B, C or N mayrandomly occupy the position of Cl, and bonds with Ti in NaCl lattice. The oxidationand carbon pollution exist on the surface of Fcc-TiBCN powder, the chief oxide is TiO2, accompanying with a small quantity of TiO, Ti2O3, B2O3.(4) The sintered TiBCN still remains a NaCl-type face-centered cubic structurewith a larger lattice parameter of4.2482. Stability of Fcc-TiBCN partat elevated temperature was exhibited as the grain size did not grow up obviously. Theexcellent sinterability of the Fcc-TiBCN powder was proved by satisfactory physicaland mechanical properties of Fcc-TiBCN part sintered at1900℃. Sintered density,microhardness, bending strength, coefficient of thermal conductivity, coefficient ofthermal expansion, electrical resistivity, Young modulus and shear modulus are4.9～5.1g·cm-3,18GPa,240～300MPa,11W/mK,8.258×10-6/K,1.5×10-6·m,423±18GPaand141±8GPa, respectively.The crystal structure of Fcc-TiBCN sintered part can’t be changed by alloyelement Al, Ni and Co, but the lattice parameter was enlarged. It was proved that thegrain could be refined obviously by addition of Al, Ni and Co. Compound Ti(Al)BCNand TiNi formed as Al substitutes Ti and Ni bonds with Ti, respectively.(5) The sintered Fcc-TiBCN part has excellent electrical machinability. Theroughness (Ra) of the machined surface by Electrical Discharge Machining (EDM) isabout0.4μm; cutting rate is about3.3mm/min. The removal mechanisms of thesintered materials dominantly included thermal stress, melting and evaporation.(6) It was revealed that hcp-TiB2precipitated from Fcc-TiBCN during sintering.hcp-TiB2have two coherent orientation relationship with Fcc-TiBCN matrix.Coherent orientation relationship is as follow:{2110}TiB2∥{112}TiBCN,{0001}TiB2∥{111}TiBCN; lattice misfit is1.08%;{0001}TiB2∥{001}TiBCN,{0110}TiB2∥{100}TiBCN, Lattice misfits are1.08%and1.55%along with [110] and[001] orientations, respectively.(7) Fcc-TiBCN powder has excellent applicability and feasibility for TIG andLaser cladding on either TC4titanium alloy or45steel. Cladding layer consisted ofcontinuous and even diffusion layer without obvious welding crack and deformation.The perfect metallurgical bond between Fcc-TiBCN powder and base metal has beenformed. The cladding layer thickness of TIG on TC4titanium alloy is about1.85～ 3.21mm. Microstructure of cladding layer reflects self-organized behavior ofFcc-TiBCN powder. TiBCN remains original Fcc crystal structure after cladding. Themorphologies of TiBCN particles in the melted metals possess various shapes such asshort rod, grain, plum blossom, feather, needle and long fasciculation, etc.Ti(Al,V)BCN have high melting point, high hardness, good corrosion resistanceformed by solution of element Al and V in Fcc-TiBCN. It is obviously shown that thehardness of matrix was increased to the highest value of1500HV appeared atsub-surface of the coated layer.