A Fuzzy Evaluation of Tool Materials in the Turning of Marine Steels

To recommend one suitable tool material for the cutting of marine steels under special conditions and requirements in emergency rescues of capsized steel ships, the cermet tools, cemented carbide tools and coated carbide tools were evaluated using a fuzzy evaluation method concerning cutting force, cutting temperature, surface roughness and tool wear. Experimental results indicate that the tool cutting performance was diverse and difficult to evaluate with a single evaluation index. The cemented carbide tools presented bad cutting performance with severe wear. Compared with the cemented carbide tools, the cermet tools showed excellent wear resistance with about 60.3% smaller tool flank wear value and good surface quality with about 46.8% smaller surface roughness. The coated carbide tools presented low cutting temperatures about 15.6% smaller than those of the cermet tools. The result of fuzzy evaluation demonstrates that the cermet tools presented the best cutting performance, followed by the coated carbide tools, and then the cemented carbide tools. The cermet tools are recommended to cut marine steels in emergency rescues of capsized steel ships.

Efficiency of Application of (Mo, Al)N-Based Coatings with Inclusion of Ti, Zr or Cr during the Turning of Steel of Nickel-Based Alloy

The article compares the properties of multilayer composite wear-resistant coatings of Zr–ZrN–(Zr, Mo, Al)N, Ti–TiN–(Ti, Mo, Al)N, and Cr–CrN–(Cr, Mo, Al)N. The investigation was focused on hardness, resistance to fracture during scratch tests, elemental composition, and structure of the coatings. Experiments were carried out to study the wear resistance of coated carbide tools during the turning of 1045 steel and of NiCr20TiAl heat-resistant nickel alloy. With the elemental compositions identical in the content of molybdenum (Mo) and aluminium (Al), identical thicknesses and nanolayer periods of λ, the coatings being studied demonstrated a noticeable difference in wear resistance. Both during the turning of steel and nickel-based alloy, the highest wear resistance was detected for tools with the Zr–ZrN–(Zr, Mo, Al)N coating (the tool life was 3–5 times higher than for uncoated tools). The good wear resistance of the Zr–ZrN–(Zr, Mo, Al)N coating may be related to the optimal combination of hardness and plasticity and the active formation of molybdenum oxide (MoO3) on the coating surface during the cutting, with good tribological and protective properties.

Comparative assessment between AlTiN and AlTiSiN coated carbide tools towards machinability improvement of AISI D6 steel in dry hard turning

AISI D6 (hardness 65 HRC) is one of the hard-to-cut steel alloys and commonly used in mould and die making industries. In general, CBN and PCBN tools are used for machining hardened steel but its higher cost makes the use for limited applications. However, the usefulness of carbide tool with selective coatings is the best substitute having comparable tool life, and in terms of cost is approximately one-tenth of CBN tool. The present study highlights a detailed analysis on machinability investigation of hardened AISI D6 alloy die steel using newly developed SPPP-AlTiSiN coated carbide tools in finish dry turning operation. In addition, a comparative assessment has been performed based on the effectiveness of cutting tool performance of nanocomposite coating of AlTiN deposited by hyperlox PVD technique and a coating of AlTiSiN deposited by scalable pulsed power plasma (SPPP) technique. The required number of machining trials under varied cutting conditions (speed, depth of cut, feed) were based on L16 orthogonal array design which investigated the crater wear, flank wear, surface roughness, chip morphology, and cutting force in hard turning. Out of the two cutting tools, newly-developed nanocomposite (SPPP-AlTiSiN) coated carbide tool promises an improved surface finish, minimum cutting force, longer tool life due to lower value of crater & flank wears, and considerable improvement in tool life (i.e., by 47.83%). At higher cutting speeds, the crater wear length and flank wear increases whereas the surface roughness, crater wear width and cutting force decreases. Chip morphology confirmed the formation of serrated type saw tooth chips.