Hardening of a quick-speed steel tool through nitration process with nitrogen controlled potential

The study of the gas nitriding method, which allows obtaining high-quality diffuse layers in high-speed steel P6M5 on the basis of an internal nitrogen hardening zone with no brittle nitride zone, has been viewed. Research results of phase composition of nitrided steel with a change in the nitrogen potential of the atmosphere during dilution of ammonia are presented. Nitrided tool increased resistance during drilling constructional steel and titanium alloy, which is due to precipitation hardening treatment of the internal nitrogenization zone using tungsten nitrides, is given.

Nitriding of High Speed Steel for Improvement of Tools Resistance

The article is devoted to the study of the gas nitriding process, which makes it possible to obtain high-quality diffusion layers in high-speed steel M2 on the basis of an internal nitriding zone without a brittle nitride zone. The results of studies of the nitrided steel phase composition with a change of the saturating atmosphere during dilution of ammonia by hydrogen are presented. An increase in the resistance of the nitrided tool when drilling structural steel is shown, which is associated with the dispersion hardening of the internal nitriding zone with tungsten nitrides.

Wear Resistance Improvement of Cemented Tungsten Carbide Deep-Hole Drills after Ion Implantation

The paper is dedicated to the lifetime prolongation of the tools designed for deep-hole drilling. Among available methods, an ion implantation process was used to improve the durability of tungsten carbide (WC)-Co guide pads. Nitrogen fluencies of 3 × 1017 cm−2, 4 × 1017 cm−2 and 5 × 1017 cm−2 were applied, and scanning electron microscope (SEM) observations, energy dispersive spectroscopy (EDS) analyses, X-ray photoelectron spectroscopy (XPS) and Secondary Ion Mass Spectrometry (SIMS) measurements were performed for both nonimplanted and implanted tools. The durability tests of nonimplanted and the modified tools were performed in industrial conditions. The durability of implanted guide pads was above 2.5 times more than nonimplanted ones in the best case, presumably due to the presence of a carbon-rich layer and extremely hard tungsten nitrides. The achieved effect may be attributed to the dissociation of tungsten carbide phase and to the lubrication effect. The latter was due to the presence of pure carbon layer with a thickness of a few dozen nanometers. Notably, this layer was formed at a temperature of 200 °C, much smaller than in previously reported research, which makes the findings even more valuable from economic and environmental perspectives.

The low coordination number of nitrogen in hard tungsten nitrides: a first-principles study

The study of the structure of the W–N system at 0–100 GPa reveals a simplified N coordination feature of the ground states, stemming from the enhanced W–N bonding.

The Process of Tungsten-Nitride Precipitation upon Nitriding Ferritic Fe-0.5 at.% W Alloy

The precipitation of tungsten nitride upon internal nitriding of ferritic Fe-0.5 at.% W alloy was investigated at 610°C in a flowing NH3/H2 gas mixture. Different tungsten nitrides developed successively; the thermodynamically stable hexagonal δ-WN could not be detected. The state of deformation of the surface plays an important role for the development of tungsten nitride at the surface. The morphologies of the tungsten nitrides developed at the surface and those precipitated at some depth in the specimen are different. The nitride particles at the surface exhibit mostly an equiaxed morphology (with the size of the order 0.5 µm) and have a crystal structure which can be described as a superstructure derived from hexagonal δ-WN. These nitride particles show a strong preferred orientation with respect to the specimen frame of reference but have no relation with the crystal orientation of the surrounding ferrite matrix. In the bulk, nanosized and finely dispersed platelet-like precipitates grow preferentially along {100}α-Fe. It is unclear whether these precipitates consist of binary iron nitride α´´-Fe16N2 or of a ternary Fe-W-N. Additionally to the finely dispersed particles, bigger nitrides at ferrite grain boundaries develop exhibiting platelet-type morphology and possessing a crystal structure which can be also described as a superstructure derived from hexagonal δ-WN. Upon prolonged nitriding assumed discontinuous precipitation of the initially precipitated finely dispersed nitrides starts from the ferrite-grain boundaries resulting in lamellas consisting of alternate ferrite and hexagonal nitride lamellas, whereas the nitride lamellas having a Pitsch-Schrader orientation relationship with the surrounding ferrite matrix. The nitrides precipitated upon nitriding in the bulk were found to be unstable during H2 reduction at 470°C. Remarkably, upon such low temperature dissolution of the nitrides took place but only the nitrogen from the nitride particles could diffuse out of the nitride platelets and the specimen, leaving W-rich regions (W-clusters) at the location of the original precipitates.