STRENGTHENING THERMO- CYCLING HEAT TREATMENT (STCHT) PROCESS OF HIGH-SPEED STEELS

Transcription

1 STRENGTHENING THERMO- CYCLING HEAT TREATMENT (STCHT) PROCESS OF HIGH-SPEED STEELS Belarussian National Technical University (BNTU) Dr. Alexander Shmatov Turin, July 4-7, 2006

2 Example of heat treated screw taps Nuts made from difficultto-cut Ni-Cr alloys Conventional heat treatment Strengthening thermocycling heat treatment (new)

3 Schematic of Traditional Heat Treatment

4 Schematic of STCHT process-1

5 Schematic of STCHT process-2

6 Schematic of STCHT process-3

7 Main purposes of this work (i) To compare and optimize the structure and properties of various grades of high-speed steels subjected to STCHT, (ii) To analyze the reasons for a simultaneous increase of different mechanical properties of high-speed steels after STCHT: high hardness and strength combined with superb fracture toughness (iii) To develop a simple, efficient and inexpensive STCHT method for cutting tools made from high-speed steels using conventional heat treatment equipment. The development of new schedules of STCHT will improve the service life and performance of high-speed steel cutting tools and permit replacing, in certain operations, more expensive hard alloys

8 Advantages of STCHT process over known heat treatments regarding properties of HSS The proposed process: Increases bending strength of HSS by 10-15%; Improves impact strength of HSS by the factor of ; Enhances surface hardness by HRC (up to HRC 67-70); Is most efficient for tools experiencing high impact loads, especially thin, fine-sized and tools for rough machining; Permits to improve productivity oftoolsbyupto30%; Can be used for processing materials with hardness HRC 40-45; Processed tools can improve the surface finish by 1-2 level;

9 Advantages of STCHT process over known heat treatments regarding structure of HSS The proposed process: Reduces the grain size of high-speed steel from up to 12; Reduces of carbide particle size by 10-15%; Increases the alloying degree of martensite by the factor of ; Permits obtaining uniform distribution of disperse carbides; Decreases of the content of residual austenite from 5-7% up to 3%.

10 Examples Results of industrial tests the increase of service life of processed tools Cutting tool type Grade of high-speed steel times mills S 6-5-2, Р6М5, Р drills S 6-5-2, Р6М5, Р18, P6M5K screw taps S 6-5-2, Р6М5, Р18, Р9М4К8PM 2-10 cutters Р6М shaping cutter Р6М reamers Р6М5, Р18, Р9М4К8PM broaches Р6М5, Р gear shaper Р6М The process is used by several enterprises in Belarus and Russia Composition of HSS: S 6-5-2, P6M5 (6% W, 5% Mo), P18 (18% W), P9M4K8 (9% W, 4% Mo, 8% Co), P6M5K5 (6% W, 5% Mo, 5% Co)

11 LOW-TEMPERATURE AND HIGH- TEMPERATURE THERMOCHEMICAL HARDENING TECHNOLOGIES FOR HARD ALLOYS Belarussian National Technical University (BNTU) Dr. Alexander Shmatov Turin, July 4-7, 2006

12 Main purposes of this work (i) To compare the structure and properties of one-, two- and three-component carbide coatings on hard alloys and optimize the composition of coatings; (ii) To develop a simple and inexpensive methods for deposition of carbide coatings onto hard-alloy cutting tools. The development of new wear resistant coating with microhardness of above 28,000 MPa, which exceeds the microhardness of silicon carbide, will improve the performance of hard alloy tools and permit processing materials with the hardness of about HRC 60.

13 Schematic of high-temperature process for producing multicomponent carbide coatings Stainless steel container Items and tools made from hard alloys Metal oxide powder mixture: 98% (50% Al 2 O % Me x O y + 15% Al) + 2%NH 4 Cl where Me x O y = Cr 2 O 3, TiO 2, V 2 O 5, MnO 2, MoO 3, Nb 2 O 5 ; Temperature: ºC. Duration: 4-6 h

14 Comparative wear resistance, microhardness and thickness of carbide coatings on hard alloys in Cr-Ti-V, Cr-Ti-Mo, Cr-V-Mo, Cr-V-Nb, Ti-V-Mo systems Type of coating Relative wear resistance criterion K w Microhardness H µ, 10 3 MPa Thickness δ, µm T15K6 BK8 T15K6 BK8 T15K6 BK8 Onecomponent Twocomponent Threecomponent Composition: T15K6 (79% WC, 15% TiC and 6% Co), BK8 (92% WC and 8% Co)

15 Reasons of high properties of multicomponent carbide coatings on hard alloys the predominance of carbides having high hardness such as TiC and VC in the coating, the formation of alloy carbides containing up to 10-15% of alloying elements the texture of carbide grains (up to 30% of the theoretical value)

16 Advantages of high-temperature process for producing multicomponent carbide coatings over known coatings The process is simple and cost-efficient due to the use of standard equipment, cheap metal oxide media which allows multiple usage, and relatively low temperature; Thorough cleaning of the surface is not required; The technology is most efficient for disposable hard alloy tools: e.g., 1 kg of the powder medium (cost $50-100) used twice permits to process 2-3 kg of hard alloy tools (cost $ ); Sintering of hard alloys can be combined with this process.

17 Results of industrial tests Examples the increase of service life of processed tools times disposable hard alloy inserts: used for final turning 4-6 used for milling 2-4 hard alloy end mills for machining steels with HRC The process is used by several enterprises in Belarus and Russia.

18 Schematic of low-temperature process for producing multicomponent carbide coatings Соntainer Hard alloy items, tools 1. Chemical treatment T=40-90 ºC 2. Heat treatment (tempering): T 130ºC Aqueous suspensions of insoluble nanosized and ultrafine carbides, nanodiamonds etc. and soluble chemical components

19 Main idea of the process To increase the service durability of cutting tools made from hard alloys using conventional equipment, cheap and ecologically safe ingredients by changing only the schedule of chemical and heat treatment operations and composition of chemical active media

20 Results of industrial tests The increase of service life of processed tools times company name screw taps (HSS) SALUT (Russia), Daewoo (Korea) 2-3 band saws (HSS) VUHZ (Czechia) drills (HSS) Stock (Germany), PS (Slovakia) end mills (HSS) BELAZ (Belarus), VST (Slovakia) knives (HSS) Skloplast (Slovakia) punches KZTS (Belarus), ZVL-LSA (Slovakia) diamond tool-grinding wheels BELAZ (Belarus) disposable carbide cutting insert used for milling and for final turning SALUT (Russia), BELAZ (Belarus) hard alloy draw plates BMZ (Belarus) bushes of dump-track BELAZ BELAZ (Belarus) The process is used by several enterprises in Belarus and Russia.

21 Advantages over known processes The process is simple and ecologically safe; After processing the dimensions of items do not change; The technology is energy-efficient: it does not require vacuum nor protective atmospheres, electric current is not required; The process is inexpensive: 1 kg of powder mixture (cost $ ) permits processing kg of tools whose cost is $ ; After resharpening, the tools retain up to 60% of wear resistance; Return-on-investment with new technologies will reach USD 1.5 to 7 per invested dollar

22 Application of new technologies The application of new technologies in industry requires minor expenses. The cost of the operation increases by only 5-15% in comparison with standard treatments. The technologies can be used on any enterprise having facilities for chemical and heat treatment and is easy to control. The processed can be used for producing tools and parts for: Power engineering Aircraft industry Instrument-making industry Automotive industry Agriculture Medicine Metallurgy Civil Engineering Household

23 Thank you for your attention! Contact Data Dr. Alexander Shmatov Belarussian National Technical University 65 Nezavisimosti Avenue , Minsk, Belarus Phone (office): ( ) Phone (home): ( ) Mobile phone: ( ) Fax: ( ) , ( )