Heat Treatment for Simulating "Damask Steel"
Development of Cost-effective Chemical Thermo-cycling Treatment Technologies of Steel Tools for Attaining Properties of Damask Steel (Combination of High Hardness, Strength and Toughness)
Tech Area / Field
- MAN-MCH/Machinery and Tools/Manufacturing Technology
- MAT-ALL/High Performance Metals and Alloys/Materials
3 Approved without Funding
Belorussian State Polytechnic Academy, Belarus, Minsk
- Physico-Technical Institute, Belarus, Minsk
- Northern Precision Engineering Ltd, UK, Wallsend\nGEE BEE GRINDING, UK, Gateshead\nArgonne National Laboratory (ANL), USA, IL, Argonne\nSnecma Moteurs / Turbomeca, France, Bordes\nNorthumbria University / Advanced Materials Research Institute, UK, Newcastle upon Tyne\nVAREBIOTEC S.A.R.L./Valorisation de Recherches en Biotechnologie, France, Meudon
Project summaryAlong with hard alloys and diamond-like materials, considerably more cheap, less brittle and better machinable tool steels are used for producing a wide variety of tools for industry, civil engineering, agriculture, medicine and life, including complex-shaped, thin, fine-sized, long-length tools, heavy-loaded and impact tools, such as milling cutters, broaches, drills, gear cutters, screw taps and threading dies, punching and bending dies, cutting rules, borers, saws, blades, knives, chisels, plows, surgical and dental tools, etc. Since the above listed tools are subject to heavy impact loading, bending and wear, they should ideally possess properties typical of "Damask steel", viz. high hardness, bending strength combined with substantial toughness.
The problem of increasing the service durability of steel tools is of vital importance. For example, annual expenditure for different cutting tools made from tool steels only on heavy hauler-producing works "BelAZ" (Zhodino, Belarus) reaches about USD 1,100,000. In machine working, the service life of cutting tools is low: for a nonstop run on a numerically controlled machine tool, it does not exceed 2 to 10 hours for milling cutters, drills and threading taps. This is why tools and not machine parts or structures are chosen as the subjects of this research. Increasing the service life of cutting tools even by a factor of 1.5 will yield substantial savings, about USD 250,000 alone for the BelAZ company.
Purpose of the project is development of cost-effective technologies of heat treatment, which will improve the service durability of steel cutting tools and stamp tools.
The main idea of the innovative technology development under the Project is to increase the service durability of complex-shaped cutting and impact stamp tools by a factor of 1.5 to 10 using conventional heat treating equipment by only changing the sequence and schedule of heat treatment operations.
Many people have heard of Damask steel. A sword made from Damask steel can cut steel nails and also bends easily. Actually, Damask steel is a composite material where the filaments of hard and soft constituents are interlaced. This brings about a unique, mutually exclusive, combination of antagonistic properties: high hardness and strength on the one hand, high fracture toughness on the other. However, the production of articles and tools from Damask steel is currently impossible since the process is too laborious, time-consuming and very expensive.
The closest properties to those of Damask steel are attained by high-temperature thermomechanical treatment of rolled stock or the surface of steel machine parts. After such processing, hardness increases by 20-50% and fracture toughness by a factor of 1.3 to 1.5, compared with standard heat treatment, which extends the service life of items by a factor of 1.1 to 2. However, high-temperature thermomechanical treatment is expensive and laborious, requires specialized equipment, and imparts insufficiently high fracture toughness to the processed items. This is why it had not found wide commercial use for extending the service life of steel tools.
In this project, a new cost-effective method of Chemical Thermo-cycling Heat Treatment of tool steels is proposed as a method that will make it possible to attain the properties of Damask steel: to increase fracture toughness by a factor of 1.5 to 15, bending strength by 10-30% and hardness by HRC 1-3, compared with standard heat treatment. This will extend the service durability of tools by a factor of 1.5 to 10.
The method of Chemical Thermo-cycling Heat Treatment includes two processes:
(i) thermo-chemical treatment, which yields case-hardening (such as carburization, nitriding, etc.), and
(ii) strengthening thermo-cyclic heat treatment which increases the strength and fracture toughness throughout the volume by cyclic heating and cooling of the steels.
Depending on the steel grade, the kind of chemical thermo-cycling heat treatment and process parameters, the method may have more than 10 versions. As a result, Chemical Thermo-cycling Heat Treatment produces a fine-grained steel structure, which substantially improves working properties.
At present, the other known methods of heat treatment do not achieve the properties of Damask steel (high hardness and strength combined with superb fracture toughness).
Modern theories of strength cannot explain the reason for an extremely high increase of fracture toughness (by a factor of up to 15) along with a 30% improvement in strength through Chemical Thermo-cycling Heat Treatment of tool steels.
Project fulfillment will help to solve an important scientific and technological problem:
attaining the properties of Damask steel in traditional tool steels and investigation of physical mechanisms responsible for the improvement of steel properties during the proposed treatment. Substantial funds, materials and equipment are required to reach these goals.
The results of the research will enable the project participants to create a new group of cost-effective technologies for the production of a wide variety of tools.
The project participants are high-skilled experts at the Belorussian State Polytechnic Academy (BSPA) and Physico-Technical Institute (PhTI) of the Belorussian Academy of Sciences. They have participated in research connected with the development of high-temperature and armor composites and equipment for rocket technologies and nuclear weapons. The BSPA scientists specialize in developing and testing Heat Treatment technologies, the PhTI scientists specialize in optimization of Heat Treatment processes, studying the properties of steels and testing tools; BSPA and PhTI scientists specialize jointly in the study of the structure of steels.
Expected results. Project fulfillment will bring about the following results:
- New methods of Chemical Thermo-cycling Heat Treatment for tool steels.
-Optimal process parameters and compositions of active media for Chemical Thermo-cycling Heat Treatment methods for tool steels providing maximum possible mechanical properties.
-Technical instructions on the developed technologies for cutting and stamp tools.
-Results of wear testing of new technologies of Chemical Thermo-cycling Heat Treatment.
In comparison with traditional heat treatment, new technologies of Chemical Thermo-cycling Heat Treatment will help to attain the following technical and economical parameters:
improvement of the wear resistance of tools by a factor of 1.5 to 10;
enhancement of the productivity of tools by up to 30%;
increasing impact toughness of steels by a factor of 1.5 to 15;
increasing bending strength of steels by up to 30%;
raising hardness by HRC 1-3 for tool steels;
enhancing the ability of tools to process materials with the hardness of HRC 40-45;
return-on-investment in using new technologies will reach USD 1.5 to 7 per invested dollar;
improvement of competitiveness of new tool products on the tool market;
The Chemical Thermo-cycling Heat Treatment technologies for various tools have the following advantages over other strengthening methods (laser or plasma treatment, vacuum coating deposition):
they are cheaper and more simple in implementation, because they can be applied in any operation which involves heat-treating facilities and they do not require additional equipment;
they are more efficient, especially for fine-sized, thin, long-length tools and impact tools;
they allow multiple resharpening of the tools owing to through hardening;
The application of new technologies of Chemical Thermo-cycling Heat Treatment of tools in industry requires minor or no expenditure.
The technologies can be implemented in many kinds of heat-treating facilities and are easy to automize. They will not lead to deterioration of ecological conditions and working environment.
Meeting with ISTC goals and objectives. The project meets ISTC goals and objectives because:
weapons scientists and engineers in Belarus will redirect their talents to peaceful activities by developing new cost-effective technologies of tool manufacturing;
the project participants integrate into the international community of Materials Scientists;
all the applied research and technology development are performed for peaceful purposes, viz. for the creation of cost-effective processes for producing efficient metal cutting and stamp tools;
it contributes to the solution of an international technical problem, viz. attaining the properties of Damask steel, i.e., a combination of antagonistic properties: high hardness and fracture toughness;
it meets the requirements of a market-based economy by creating new competitive technologies (simple, efficient and cost-effective) of tool production for civil needs.
The work program includes solving 4 interconnected tasks, the essence of which includes:
(1) comparative analysis and elaboration of new methods of Chemical Thermo-cycling Heat Treatment of tool steels imparting to them a combination of high mechanical properties;
(2) optimization of Chemical Thermo-cycling Heat Treatment regimes with respect to the structure and mechanical properties of tool steels;
(3) development of new technologies for cutting and stamp tools;
(4) wear testing of the developed Chemical Thermo-cycling Heat Treatment technologies.
Participating organizations (for all tasks of the project) are BSPA and PhTI.
The Advanced Materials Research Institute of the University of Northumbria at Newcastle, Great Britain, has supported the project as Collaborator. Cooperation with this Collaborator envisages:
joint discussion of project results;
meeting at conferences;
The risk of fulfilling the Project is reduced to minimum since, at present, the results of one of the Chemical Thermo-cycling Heat Treatment versions was tested on 3 grades of tool steels. For example, for carbon tool steel containing 0.8% C with a hardness of HRC 59-60, after this treatment the impact toughness of specimens improved by a factor of 13 to 15 and the bending strength increased by up to 30%, as compared with traditional heat treatment.
At present, about 20 tool-producing companies and Research Institutes in Germany, Austria, USA, Great Britain, Denmark, Sweden, France, South Korea, India, Poland and other countries have expressed their interest in the development of Chemical Thermo-cycling Heat Treatment technologies.
New Chemical Thermo-cycling Heat Treatment technologies are patentable because their technical level (fracture toughness and strength characteristics of tool steels) will exceed the level attained by the best modern foreign processes.
The project participants, together with Collaborators, plan to patent the developed technologies in many industrial countries.