Composição, estrutura e propriedades do metal duro
Composition: the main components of cemented carbide are WC, CO and tic, and the secondary components are tin, Ni, Mo, TAC, NBC, VC, Cr3C2, etc. Among them, WC (including TIC) accounts for more than 80% and co accounts for less than 20%. The proportion of other components is very small.
Structure: the normal structure of tungsten cobalt alloy is the two-phase structure of WC phase and co phase. The former is also called hard phase or α Phase, the latter is adhesive phase or β Phase. There are two normal structures of tungsten titanium cobalt alloys, one is (Ti, w) c+co two-phase structure, and the other is (Ti, w) + wc+co three-phase structure.
Performance: the main performance indicators of cemented carbide include density, bending strength, hardness, coercive force, cobalt magnetism, etc. Density is the most basic index of cemented carbide quality, and it is the basis of other properties. Hardness and bending strength are the two main mechanical properties of cemented carbide, which directly affect the application effect of the alloy. These three properties basically determine the comprehensive quality of cemented carbide, which is not only the evaluation index of products leaving the factory, but also the index that users pay most attention to, and an important basis for the rational selection of cemented carbide.
Funções de várias substâncias comumente usadas em materiais de ferramentas:
WC – fase resistente ao desgaste, principal componente do material da ferramenta;
Co – fase dúctil, com o aumento do teor de CO, a resistência e a tenacidade da liga aumentam e a dureza diminui;
TiC – fase dura, com o aumento do teor de TiC, a capacidade anticraterase da liga aumenta, mas a resistência e a tenacidade da liga diminuem e a fragilidade da liga aumenta;
TAC, NBC – fase dura, que pode melhorar significativamente o desempenho em altas temperaturas e a resistência ao desgaste da liga. A liga com TAC e NBC tem boa versatilidade;
CRC, VC inhibitor, inhibiting WC grain growth
According to different compositions, cemented carbides can be divided into five categories.
- Tungsten carbide based cemented carbide: including WC Co, WC tic Co, WC TAC Co, WC tic tac (NBC) -co, etc. These alloys are mainly composed of WC.
- Titanium carbide based or titanium carbonitride based cemented carbide: a kind of cemented carbide usually composed of tic or Ti (C, n) as the basic component and Ni Mo as the binder. Such as tic Mo Ni, tic WC TAC (NBC) -mo Ni, Ti (C, n) -mo Co Ni, etc.
- Coating cemented carbide: deposit a layer of tic, tin, TiB2, ZrN, CrN, AI2O3, TiCN, B4C, SiC, BN, TiAIN, diamond and other substances on the alloy surface, so as to double the service performance of the tool.
- Steel bonded cemented carbide: a kind of cemented carbide whose main component is steel and whose hard phase is tic or WC. Its remarkable feature is that it can be heat treated and machined. It is a kind of intermediate alloy between tool steel and cemented carbide.
- Other cemented carbide: such as Cr3C2 based cemented carbide, which is composed of Cr3C2 as the main component and Ni or Ni-W as the binder. It is usually used as wear-resistant and corrosion-resistant parts.
- Além disso, existem dois materiais de ferramentas importantes. Um deles são os materiais cerâmicos, incluindo alumina (cerâmica branca), nitreto de silício e cerâmica Theron (si3n4/al2o3). O outro são os materiais superduros, o diamante policristalino (PCD) e o nitreto de boro cúbico policristalino PCBN.