INFLUENCE OF COLD NITROGEN GAS AND OIL MIST IN MACHINING NICKEL-BASE K424 ALLOY WITH CERAMIC CUTTING TOOLS

The role of cold nitrogen gas and oil mist on tool wear and surface roughness is investigated in turning the K424 nickel-base super alloy with Sialon and SiC whisker-reinforced alumina ceramic tools. A new cooling system is developed and used to lower the temperature of the compressed nitrogen gas. Experiments are performed in three different cooling/lubrication modes, i.e. the dry cutting, the cold nitrogen gas （CNG）, and the cold nitrogen gas and oil mist （CNGOM）. Experimental results show that the depth-of-cut notching severely limits the tool life in all the cooling/lubrication modes. Compared with the dry cutting, the use of CNG and CNGOMcan yield higher wear rate of depth-of-cut notching and worse surface finish.

Synergistically Toughening Effect of SiC Whiskers and Nanoparticles in Al_2O_3-based Composite Ceramic Cutting Tool Material

In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties. While no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening effects of them have not been studied. An Al2O3-SiCw-SiC np advanced ceramic cutting tool material is fabricated by adding both one-dimensional SiC whiskers and zero-dimensional SiC nanoparticles into the Al2O3 matrix with an effective dispersing and mixing process. The composites with 25 vol% SiC whiskers and 25 vol% SiC nanoparticles alone are also investegated for comparison purposes. Results show that the Al2O3-SiCw-SiCnp composite with both 20 vo1% SiC whiskers and 5 vol% SiC nanoparticles additives have much improved mechanical properties. The flexural strength of Al2O3-SiCw-SiCnp is 730＋ 95 MPa and fracture toughness is 5.6 ± 0.6 MPa.m1/2. The toughening and strengthening mechanisms of SiC whiskers and nanoparticles are studied when they are added either individually or in combination. It is indicated that when SiC whiskers and nanoparticles are added together, the grains are further refined and homogenized, so that the microstructure and fracture mode ratio is modified. The SiC nanoparticles are found helpful to enhance the toughening effects of the SiC whiskers. The proposed research helps to enrich the types of ceramic cutting tool and is benefit to expand the application range of ceramic cutting tool.

Microwave synthesis of duplexα/β-SiAlON ceramic cutting inserts:Modifying m,n,z values,synthesis temperature,and excess Y_(2)O_(3) synthesis additive

Duplexα/β-SiAlON ceramic cutting inserts(30α:70β)were synthesized by microwave sintering.The effects of solid solution parameters(m,n,z),synthesis temperature,and amount of excess Y_(2)O_(3) synthesis additive on phase assemblage,microstructure,mechanical properties,and cutting performance were systematically investigated.It was found that increasing m value could improve the formation ofαphase while high z value over 1.0 resulted in the dissolution ofαphase intoβphase and intergranular phase.Increasing the amount of excess Y_(2)O_(3) could promote densification and elongatedβgrain growth;however,the excess Y_(2)O_(3) amount above 4 wt%resulted in substantial crystallization of M'SS phase,thus declining the mechanical properties and wear resistance.The microwave-synthesizedα/β-SiAlON cutting insert with modified parameters(m=1.7,n=1.0,z=0.7,and 3 wt%excess Y_(2)O_(3))was obtained with optimal comprehensive properties,whose tool life was found to increase by approximately 75%in high-speed milling of Inconel 718 superalloy compared to the commercialα/β-SiAlON cutting insert.

Rare earth ceramic cutting tool and its cutting behavior when machining hardened steel and cast iron

The addition of rare earth element yttrium played an important role in the improvement of both mechanical properties and wear resistance of Al2O3/(W,Ti)C ceramic cutting tool material.Mechanical properties especially the fracture toughness and flexural strength were obviously increased when a suitable amount of the yttrium were added.Wear resistance of the developed rare earth ceramic cutting tool material was higher than that of the corresponding materials without rare earth in the machining of the hardened 45# carbon steel and cast iron HT20-40.Wear modes of the Al2O3/(W,Ti)C rare earth ceramic tool materials were mainly flank wear and crater wear accompanied with slight notch wear when machining the hardened carbon steel.Wear mechanisms were major abrasive wear at low cutting speed and adhesive wear at high cutting speed.Wear modes were nearly the same except that the adhesion phenomenon in the crater area was intensified when machining cast iron.The flank wear area was relatively smooth with no obvious plowing phenomenon which was possibly concerned with the workpiece of low hardness and the adhesion phenomenon at high cutting temperature.

MULTI-SCALE AND MULTI-PHASE NANOCOMPOSITE CERAMIC TOOLS AND CUTTING PERFORMANCE

An advanced ceramic cutting tool material Al2O3/TiC/TiN （LTN） is developed by incorporation and dispersion of micro-scale TiC particle and nano-scale TiN particle in alumina matrix. With the optimal dispersing and fabricating technology, this multi-scale and multi-phase nanocomposite ceramic tool material can get both higher flexural strength and fracture toughness than that of A1203/TiC （LZ） ceramic tool material without nano-scale TiN particle, especially the fracture toughness can reach to 7.8 MPa . m^0.5. The nano-scale TiN can lead to the grain fining effect and promote the sintering process to get a higher density. The coexisting transgranular and intergranular fracture mode induced by micro-scale TiC and nano-scale TiN, and the homogeneous and densified microstructure can result in a remarkable strengthening and toughening effect. The cutting performance and wear mechanisms of the advanced multi-scale and multi-phase nanocomposite ceramic cutting tool are researched.

NOTCH WEAR OF MACHINING NICKEL BASED ALLOYS WITH CERAMIC TOOLS

The performances of mixed ceramic and sialon ceramic tools in machining nickel based alloy are tested.The negative cutting edge inclination and small tool lead angle are recommended for reducing ceramic tool failure. So called“notching at depth of cut”is not actually at the depth of cutting line, but out of cutting area。 The real reason of notching is caused by shocking of “sawtooth”on sawtooth- shaped burr and fin- shaped edges of chip

Brief Introduction of Zang Jian

Zang Jian,also known as Wang Danqing,was born in the 1970s.Arts Agencies She was CEO of Nuo Bei Education and Culture Co.,Ltd,and art Chief Inspector of Qingdao.Federation of the Handicapped.She is keen on painting,writing and art review.Her abstract Chinese paintings,