Khriashchova Mariia

Faculty: Fiziko-metallurgical
Speciality:Thermal processing

Theme of master's work:

The investigation of the structure and properties of hard alloy on the basis of titanium carbide, which was got by a method of hot vacuum compressing

Scientific adviser: Pashynskyy Volodymyr Victorovich

Summary of research and developments

Alloys on the basis of titanium carbide with nickeliferous bond having prospects for turning rollers production in exchange for tungsten ones. But the complete replacement of tungsten carbide in the content of hard alloy metals by titanium carbide requires the development and application of such metal bonds which along with the high hardness and strength will possess the improved ductility property.
The researches were carried out on the alloys specimens Т50Н10Ж and Т50Н40Ж, Т35Н19Ж46(marking alloys is given in accordance with Ukrainian standards), which possess the following chemical compound: Т50Н10Ж: TiC=50%; Ni=10%; other iron;
Т50Н40Ж: TiC=50%; Ni=40%; other iron;
Т35Н19Ж46: TiC=35%; Ni=19%; Fe=46%.

As a test sample the alloy on the basis of tungsten, titanium, tantalum and cobalt carbide bond was used. There was elected the alloy ТТ7К12, which has the following chemical compound:
WC=81%; TiC=4%; ТаС=3%; Co=12%.
The assumed thermal work conditions of wire addition system rollers from those materials were simulated on the proposed samples.
After 2hours soaking at 700 °С and etching at 530-540°С during 15 minutes the shot of microstructure was made on the specimen ТТ7К12 (Fig. 1а).
The heating of the rest specimens was carried out up to 600°С, 700°С, 800°С and 900°С. The soaking duration was 2 hours at each temperature. The visible results were achieved only at the heating up to 900°С, and then the observable dense film of oxides was appeared on the whole three specimens.
The slices made on the samples with help of diamond paste on wooden substrate layer polishing, and then the thermal etching Т50Н10Ж was made at 570-580°С during 30 minutes (Fig. 1b).Т50Н40Ж -was made at 750-760°С during 30 minutes (Fig. 1c), Т35Н19Ж46 - was made at 570-580°С during 15 minutes (Fig. 1d).

а	б	в	г

According to the given results one can make the following conclusion:
1. The conducted comparative evaluation of the cutter ТТК and test samples Т50Н10Ж, Т50Н40Ж, Т35Н19Ж46 showed the distinct advantage of the last ones; during the continuous working at the temperature 700°С the specimen of the cutter starts intensively to oxidize.
2. On the received microstructures it’s obvious that the alloy Т35Н19Ж46 is the most intensively oxidized in comparison with the alloys Т50Н10Ж and Т50Н40Ж that point to the fact that the metal bond starts to oxidize the first one.
3. Т50Н10Ж in comparison with Т35Н19Ж46 has practically the same content of iron but is not gas corroded such intensively. That’s the result of the structure full of titanium carbides which in their turn are the «barriers» for the oxidation.
4. It follows from the presented materials that the alloy Т50Н40Ж possess the maximal resistance to corrosion owing to the low content of metal bond and high content of nickel.

Literature

1. Катрич в.Г. Исследование структуры и свойств твердых сплавов для прокатных валков [Электронный ресурс] - http://masters.donntu.ru/2006/fizmet/katrich/diss/index.htm
2. Киффер Р., Бенезовский Ф. Твердые сплавы. [Текст] - М.:Металлургия, 1971. - 196с.
3. Панов В. С., Чувилин А.М. Технология и свойства спеченных твердых сплавов и изделий из них.[Текст] – М.:Миссис, 2001. – 216с.
4. ГОСТ 9391 – 80 «Сплавы твердые спеченные. Методы определения пористости и микроструктур».[Текст]
5. ГОСТ 3882 – 74 «Сплавы твердые спеченные. Марки».[Текст]