Infiltration temperature controlling is crucial in the process of tungsten copper electrode, its rise and fall has a great effect on comprehensive performance of tungsten copper electrode. There is a graph of infiltration temperature effect on W-25Cu tungsten copper density as follow.

Take W-25Cu tungsten copper electrode as an example, the density of tungsten copper electrode increases with the increasing infiltration temperature in the beginning. When the temperature reaches 1350 ℃, it reaches highest density (14.84g/cm3). However, when the temperature exceeds 1350 ℃, the density tungsten copper electrode decreased. This is because one of the basic conditions necessary for infiltration is infiltration requirements can be well wetted metal matrix material, i.e. 0 ° <θ <90 ° (θ copper and tungsten wetting angle). And smaller θ and the more conducive to infiltration process.

Infiltration is the most widely used in tungsten copper electrode manufacturing so that the study on mechanism of tungsten copper electrode is also important. However, not any two kinds of metal can be used in infiltration.

There are some essential basics for tungsten copper infiltration:

1. Infiltrated metal (Cu) can wet the skeleton material (W) completely.

2. There is a great difference of melting point between skeleton material (W) and infiltrated metal (Cu) in case of the deformation of parts.

3. The solubility of the skeleton (W) and infiltrated metal (Cu) should be low or immiscible so that the liquid phase will disappear when the compounds or solid solution emerging after the reaction.

4. The amount of infiltrated metal (Cu) should be limited by fill-in the pores, more or less will have negative influence.

More infomation about  tungsten copper electrode infiltration mechanism, click here:

http://news.chinatungsten.com/en/tungsten-information/80768-ti-10409 
http://news.chinatungsten.com/en/tungsten-information/80801-ti-10412

Spontaneous infiltration filled the porous tungsten matrix with molten copper solution by means of capillary force rather than the diffusion of atoms. Viewed from the mechanism of capillary, the gravitational potential energy of the capillary liquid should come from inside the liquid molecules into the adhesive layer for the loss of potential energy. Because the potential energy in the adhesion layer should be smaller than in the liquid inside, according to the potential energy minimum principle in stable equilibrium, the molecules inside the liquid have to squeeze into the adhesive layer so that the adhesive layer has a tendency to stretch.

The potential higher copper solution continuously into the inner molecular layer attached to the lower potential, the molecules will keep the potential loss of gravitational potential energy is converted into the molecule, so the liquid rising in the capillary.

More infomation about  tungsten copper electrode infiltration mechanism, click here:

http://news.chinatungsten.com/en/tungsten-information/80768-ti-10409

In last part we know that tungsten carbide end mills with (Ti,Al)N, (Ti,W)N/(Ti,W,Si)N, and (Ti,W)N/(Ti,W,Si,Al)N coating films will be tested to know the tool wear, because the exact features of new titanium/tungsten/silicon/aluminum-based coating films are still unknown for cutting hardened steel. Here in this part we explain the experimental procedures.

2. Experimental Procedures

The work material used was hardened steel (AISI D2,60HRC). The chemical composition of the hardened steel is shown in Table 1. The tool material of the substrate was cemented carbide, and three types of PVD-coated cemented carbide were used as shown in Table 2. Namely, the coating films used were (Ti,W)N/(Ti,W,Si)N and (Ti,W)N/(Ti,W,Si,Al)N coating film. (Ti,W,Si,Al)N is a new type    of coating film.  (Ti,W)N/(Ti,W,Si)N and (Ti,W)N/(Ti,W,Si,Al)N comprise a multilayer coating system.

The inner layer of the (Ti,W)N/(Ti,W,Si)N and (Ti,W)N/(Ti,W,Si,Al)N coating system is (Ti,W)N coating film, and  the outer layer is (Ti,W,Si)N and (Ti,W,Si,Al)N coating films, respectively. Furthermore, commercial (Ti,Al)N-based coating film was also used as the (Ti,Al)N.

(To be continued. This article is divided into several parts. Here is part 6. For part 5 please refer to http://news.chinatungsten.com/en/tungsten-information/80796-ti-10487)

In last part we know that tungsten carbide tools with (Ti,W,Si)N coating film are better in wear resistance, hardness and critical scratch load, and so is maybe more effective material for cutting hardened steel. Here in this part we explain why we choose (Ti,Al)N, (Ti,W)N/(Ti,W,Si)N, and (Ti,W)N/(Ti,W,Si,Al)N coating films as the testing materials.

Furthermore, new titanium/tungsten/silicon/aluminum-based coating       films, namely (Ti,W,Si,Al)N, (Ti,W,Si,Al)C, and (Ti,W,Si,Al)(C,N) coating film, have been developed. However, it is not clear whether these coating films are effective tool materials for milling hardened steel.

In this study, hardened steel was milled with three physical vapor deposition (PVD)-coated cemented tungsten carbide end mills in order to clarify effective tool materials for cutting hardened steel at high cutting speeds. The coating films used were (Ti,Al)N,         (Ti,W)N/(Ti,W,Si)N,   and (Ti,W)N/(Ti,W,Si,Al)N coating film. The tool wear was experimentally investigated.

(To be continued. This article is divided into several parts. Here is part 5. For part 4 please refer to http://news.chinatungsten.com/en/tungsten-information/80792-ti-10486; for part 6, please refer to http://news.chinatungsten.com/en/tungsten-information/80797-ti-10488)

Ammonium paratungstate (or APT) is a white crystalline salt of ammonium and tungsten, with the chemical formula (NH₄)₁₀(H₂W₁₂O₄₂)·4H₂O.

Ammonium paratungstate is produced by separating tungsten from its ore. Once the ammonium paratungstate is prepared, it is heated to its decomposition temperature, 600 °C. Left over is WO₃, tungsten(VI) oxide. From there, the oxide is heated in an atmosphere of hydrogen, reducing the tungsten to elemental powder, leaving behind water vapor. From there, the tungsten powder can be fused into any number of things, from wire to bars to other shapes.

In this research, the possibility of mechanochemical decomposition of ammonium paratungstate (APT) has been studied, and compared with thermal decomposition method. For this purpose, APT powders were milled using a planetary ball mill up to 36 hours and under air atmosphere. For thermal decomposition, APT powders were heated for 30 minutes at 300 and 450°C in air atmosphere. X-ray diffraction (XRD), differential scanning calorimeter (DSC), and thermo gravimetric analyzer (TGA) were used to study the decomposition progress, and products. The XRD results showed that APT completely decomposed to WO3 by thermal decomposition, while the final product of mechanochemical decomposition was WO3 (H2O)0.5. According to DSC and TGA results, during thermal decomposition, ammonia and water released in four steps, and leaved WO3. By mechanochemical decomposition crystal water and ammonia liberated from APT structure, but structural water of APT remained. In both methods, an X-ray amorphous phase was the intermediate product of APT decomposition.

In last part we know that tungsten carbide tools with (Ti,W)N coating film have superior critical scratch load to high speed cutting hardened steel in mass production. Here in this part we explain the superior quality of (Ti,W,Si)N coating film.

Moreover, the titanium/tungsten-based-coated tungsten carbide tool was evaluated through machining of low-carbon steel AISI 5120H, and showed greatly improved performance. However, the hardness of the (Ti,W)N coating film was lower than that of the (Ti,Al)N coating film. So, a (Ti,W,Si)N coating film, which is a titanium/tungsten/silicon-based   coating film, has been developed.

This titanium/tungsten/silicon-based coating film exhibits both superior critical scratch load and hardness compared with TiN/(Ti,Al)N coating film. In cutting AISI 5120H, the wear progress of the (Ti,W,Si)N-coated cemented tungsten carbide tool is slower than that of the TiN- and (Ti, Al)N-coated tools. Therefore, titanium/tungsten/silicon coating is an effective tool material because it has good wear resistance.

(To be continued. This article is divided into several parts. Here is part 4. For part 3 please refer to http://news.chinatungsten.com/en/tungsten-information/80791-ti-10485; for part 5, please refer to )

In last part we know that tungsten carbide end mills with (Ti,W,Si,Al)N coating film have the least tool wear at speed of below 3.33 m/s in cutting hardened steel. Here in this part we explain the superior quality of (Ti,W)N coating film.

1. Introduction

Hardened steels used for dies or molds are widely cut as a substitute for grinding. Polycrystalline cubic boron nitride (cBN) compact tools are used for cutting hardened steels, due to their higher hardness and higher thermal conductivity. However, in milling, major tool failure of cBN readily occurs by fracture because cBN has poor fracture toughness. Coated cemented tungsten carbide is an effective tool material for milling hardened steels because it has good fracture toughness and wear resistance. The physical vapor deposition (PVD) method is a widely used coating technology because of its lower treatment temperature, namely 470 K -870 K.

Recently, it has become possible to cut hardened steels with (Ti,Al)N-coated tungsten carbide cutting tools. However, as machine parts are often cut at higher cutting speeds for mass production, tool materials must have excellent fracture toughness and wear resistance. A titanium/tungsten-based coating film, namely (Ti,W)N coating film, has been developed. Titanium/tungsten-based coating film exhibits a superior critical scratch load.

(To be continued. This article is divided into several parts. Here is part 3. For part 2 please refer to http://news.chinatungsten.com/en/tungsten-information/80790-ti-10484; for part 4, please refer to http://news.chinatungsten.com/en/tungsten-information/80792-ti-10486)

In last part we know that tungsten carbide end mills with (Ti,W,Si)N and (Ti,W,Si,Al)N coating films will be tested to determine the best materials for cutting hardened steel. Here in this part we give the results to be reached in this article.

The following results were obtained:

(1) In milling hardened steel at a cutting speed of 3.33 m/s, the tool wear width of the (Ti,W)N/(Ti,W,Si,Al)N-coated tungsten carbide end mill was smaller than that of the (Ti,W)N/(Ti,W,Si)N-coated one. And, compared with the commercial (Ti,Al)N, the tool wear width of the (Ti,W)N/(Ti,W,Si,Al)N-coated tool was smaller than that of the (Ti,Al)N-coated tool.

(2) The tool wear of the (Ti,W)N/(Ti,W,Si,Al)N-coated tool increased with an increase in cutting  speed.

(3) The cemented carbide with (Ti,W)N/(Ti,W,Si,Al)N coating film was an effective tool material for high-speed cutting below a cutting speed of 3.33 m/s.

(To be continued. This article is divided into several parts. Here is part 2. For part 1 please refer to http://news.chinatungsten.com/en/tungsten-information/80788-ti-10483; for part 3, please refer to http://news.chinatungsten.com/en/tungsten-information/80791-ti-10485)

Ammonium paratungstate (or APT) is a white crystalline salt of ammonium and tungsten, with the chemical formula (NH₄)₁₀(H₂W₁₂O₄₂)·4H₂O.

Ammonium paratungstate is produced by separating tungsten from its ore. Once the ammonium paratungstate is prepared, it is heated to its decomposition temperature, 600 °C. Left over is WO₃, tungsten(VI) oxide. From there, the oxide is heated in an atmosphere of hydrogen, reducing the tungsten to elemental powder, leaving behind water vapor. From there, the tungsten powder can be fused into any number of things, from wire to bars to other shapes.

A process is disclosed for producing ammonium paratungstate which involves adding hexamethylenetetramine to a first solution of ammonium tungstate, adjusting the pH to about 2 with an acid to form a precipitate which contains the major portion of the tungsten and the hexamethylenetetramine and separating the precipitate from the resulting mother liquor. The tungsten hexamethylenetetramine precipitate is then dissolved in aqueous ammonia to form a second ammonium tungstate solution which is then heated at from about 90℃ to about 100℃ to form a precipitate essentially all of which is ammonium paratungstate and a mother liquor which contains essentially all of the hexamethylenetetramine. The ammonium paratungstate precipitate is then separated from the mother liquor.