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The susceptibility of wood-cutting tools to corrosive wear
Wear, 74 (1981-
85
1982) 85 - 92
THE SUSCEPTIBILITY WEAR*
OF WOOD-CUTTING
TOOLS
TO CORROSIVE
GANDI D. MOHAN and BARNEY E. KLAMECKI Forest Products Laboratory,
University of California, Richmond,
CA (U.S.A.)
(Received April 6,198l)
Summary
The machining of green (wet) wood results in unique cutting tool problems. The non-homogeneous multicomponent nature of cutting tools and the water and water solubles in the wood result in electrochemical action. Both mechanical and corrosive tool wear mechanisms are thus active in such wood cutting, The relative magnitudes of mechanical and electrochemical effects were determined by analyzing tool life data in terms of simple models of the individual wear mechanisms. It was demonstrated that under conditions conducive to electrochemic~ action the major part of the total wear was due to corrosion. Some of the factors determining the corrosion susceptibility of cemented carbide tools were studied by measuring the electrical potentials developed between tool components in solutions typical of those found in various woods. The results of these tests indicate that electrochemical action can be influenced by changing the tool binder material, the relative percentage of the tool binder material in the tool and the carbide grain size,
1. Introduction
In most rnate~~-cutting operations, several tool wear mechanisms act simultaneously. Total tool wear is the result of the combined actions and interactions of all the active wear mechanisms. A unique tool wear situation arises in the cutting of green (undried) wood. In these operations the workpiece is composed of the wood substance, water and water solubles characteristic of the tree species. In contrast with mew-cutting operations where the use of an engineered cutting fluid should improve the tool performance, in wood cutting the liquid component of the wood is uncontrollable: its
*Paper presented at the International Conference on Wear of Materials 1981, San Francisco, CA, U.S.A., March 30 - April 1, 1981. 0043-1648/81j0000~0000/$02.50
@ Elsevier Sequoia~~nted
in The Netherlands
86
effect on tool life may be beneficial or detrimental. There is evidence that the liquid component in wood and the non-homogeneous nature of cutting tools give rise to electrochemical effects in the work--chip-tool contact region [l] . The extent of these electrochemical effects, the factors controlling them and their effect on cutting tool wear are the subjects of this paper. Cutting tool life tests and electrochemical test cell results were analyzed with the intent of determining the corrosion susceptibility of cemented carbide tools used to cut wet wood. The extent of electrochemically induced wear and some of the factors which might control the rate of electrochemical action were studied.
2. Background Perhaps the earliest reported works on electrochemical effects in wood cutting are those of Kivimaa [2] and Alekseev [3] . By applying an electrical potential to the cutting tool, large changes in tool life were produced. Increased or decreased rates of wear resulted, depending on the relative tool-work polarity. Hillis and McKenzie [4] reported etching of steel tools when solutions typical of those in eucalyptus were placed on the tools. Kirbach and Chow [ 51 immersed cemented carbide tools in red cedar solutions and produced scanning electron micrographs which show that the cobalt binder is preferentially removed from the tools. The existence of the action of an electrochemical wear mechanism in cutting green wood is emphasized by Klamecki [l] . Significant decreases in tool wear were produced by electrically insulating the cutting tool from the lathe in turning tool life tests. Although the existence of electrochemical effects in wood-cutting tool wear has been demonstrated, the relative magnitude of these effects compared with mechanical wear mechanisms has been studied only recently [6] . The factors controlling the rate of electrochemical action have not been studied.
3. Magnitude of electrochemical
wear relative to mechanical wear
The results of tool life tests in lathe turning are presented in Fig. 1. The tool life T was defined as the cutting time necessary to cause 45 pm of flank wear on the high speed steel and cemented tungsten carbide tools used. A depth of cut of 2.54 mm and a feed of 0.25 mm rev-l were chosen so that, with the relatively low cutting speeds used, only insignificant changes in the thermal and mechanical environments near the cutting edges were expected. Simple models of mechanical and electrochemical wear mechanisms developed by Tsai and Klamecki [ 61 can be applied to these tool life data. If a mechanical wear mechanism in which the amount of tool wear is directly proportional to the length of tool-work sliding is postulated, and if no changes in the tool-work interactions occur over the cutting speed range
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Fig. 1. The results of tool life tests in which water-saturated wood (0), air-dried wood ( X), ponderosa pine (- - -) and incense cedar ( -) were turned using high speed steel and cemented carbide tools.
used, the slope of the log V-log 2’ plot will be unity (V is cutting speed and T is tool life). The cutting of air-dried wood yields this result. When watersaturated wood is cut, the tool life is less dependent on cutting speed. Additional wear mechanisms which are independent of cutting speed are then sought to explain the test results. The amount of tool wear caused by electrochemical action is expected to be dependent on the length of time of tool-work contact and not on the cutting velocity. This interpretation can explain the insensitivity of tool wear to cutting speed changes in cutting incense cedar which is a very acidic wood. That is, in the continuous cutting of acidic woods at relatively low cutting speeds, a large part of the total tool wear is due to electrochemical action between the tool and work material. This is reflected in Fig. 1 by the large value of the slope )71for the tool life tests in cutting wet incense cedar with high speed steel tools and by the differences in tool life when green and air-dried woods are cut.
4. Investigation
of the corrosion susceptibility
of cemented carbide tools
4.1. Proposed mechanism of electrochemical wear The demonstration that, in certain wood-cutting situations, corrosion may account for a large part of the wear of the cutting tool raises several questions. From an applications point of view, perhaps the most important question is which factors control the corrosion susceptibility and corrosion rate of cemented carbide tools used to cut wet wood. The multicomponent natures of the carbide cutting tool and the work material are expected to lead to mechanical and electrochemical actions which result in tool wear. The electrochemical part of the wear is modeled as shown in Fig. 2. It is expected that the tool binder material will be anodic and go into solution with the movement of electrons to the carbide component; this is followed by the discharge of this cathode with the formation of hydrogen gas. An
88 Water
Fig. 2. The electrochemical action proposed to explain the corrosive wear of cemented carbide cutting tools used to machine wet wood.
adequate explanation of this process requires an expression relating the rate of electrochemical action to the characteristics of the tool and work materials, i.e. a description of the tool-work infractions. As a first step in this direction the corrosion susceptib~ities of cemented carbide tool components in conditions approximating wood cutting were determined. When two different metals are joined in an electrolytic solution the potential for corrosion is related to the electrical potential which exists between them. Referring to the model of the wood-cutting operation in Fig. 2, it is expected that the important factors determining corrosion susceptibility are the materials present and their distribution. The material considerations are the hard phase and binder materials in the tool and the pH and chemical composition of the electrolyte supplied by the work material. In addition the relative surface areas of the carbide grams and binder which are related to the grain size and the volume percentage of binder will probably be important. With this rationale an attempt was made to characterize the corrosion susceptibility of cemented carbide tools by measuring the electrical potential developed between the component materials when exposed to electrolyte solutions typical of those found in wood. This was done by suspending specimens of the tool component materials in solutions derived from different woods and measuring the electrical potential developed between the specimen and a standard electrode. For this initial work the effects of changing stress and temperature fields in tools during cutting were not investigated. 4.2. Exp~rirnen~~~ procedure The test specimens were made by gluing tungsten carbide particles and cobalt, nickel and iron powders onto cylindrical stainless steel rods using electrically conducting epoxy. The tungsten carbide particles were of 1.5, 6.5,10 and 25 pm sieve size. The electrolyte solutions were prepared by soaking wood chips in distilled water (0.110 kg of chips per liter) at 65 “C for 24 h. The woods used were white fir, which yielded a solution with a pH of approximately 5.0, California black oak (of pH about 3.7) and incense
89
cedar (of pH about 3.1). Each of the specimens was suspended in a glass electrolytic test cell containing the test solutions, and its potential with respect to a standard graphite electrode was measured over a period of 1 h. 4.3. Resu2ts Figure 3 shows the changes with time of the test electrode potentials (with respect to a standard electrode) of tungsten carbide electrodes made from two sizes of tungsten carbide particles in the three test solutions, The values shown are the average of ten tests. After approximately 30 min there was essentially no change in the measured potentials. The roles of the carbide grain size, the tool component material and the solution characteristics in determining the electrode potential are indicated in Figs. 4 and 5. The potentials presented in these figures are those measured after 30 min of immersion and represent the average of five tests. Figure 4 shows that, at tungsten carbide grain sizes larger than about 6 (urn, the grain size has little effect on the measured potential. The use of 1.5 pm particles resulted in potentials which were much larger than those measured using electrodes made from larger particles. The potential differences measured in the different test solutions shown in Figs. 3 and 4 are closely related to the difference in the pH values of the 100
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Fig. 3. The potential between tungsten carbide and graphite electrodes in solutions derived from white fir (F), black oak (0) and incense cedar (I) for two different sizes of tun~ten carbide grains. Fig. 4. The potentials developed between graphite and tungsten carbide electrodes made from carbide particles of varying size in solutions derived from white fii (F), incense cedar (I) and black oak (0).
90
Fig. 5. The test electrode potentials with respect to graphite electrodes for tungsten carbide (W) and binder material (C, cobalt; N, nickel; R, iron) electrodes in solutions of varying pH. The tungsten carbide specimens were made from 1.5 pm grains.
solutions. This is shown, together with the potential differences between the tungsten carbide and possible binder metals, in Fig. 5. The potentials of the test electrodes near a pH of 5 are from measurements made in white fir solutions, those between pH values of 3.5 and 4.0 are from black oak solution tests and those near a pH of 3.0 are from the incense cedar solutions. Solutions with a lower pH resulted in lower measured test electrode potentials (with respect to a standard electrode) and this effect was greater for cobalt and nickel than for tungsten carbide. The difference between the rates of change in potential with pH for the different metals tested means that the difference between the potential of the tungsten carbide and the other metals tested varies with the solution pH. For example the change in the WC-Co potential with decreasing pH is greater than the change in the WC-Ni potential.
5. Discussion There is evidence that, when wet wood is cut, electrochemical factors affect the overall cutting tool wear. In some cases, e.g. the continuous cutting of acidic wood, electrochemical action may account for the major portion of the total tool wear. Tool life cutting tests do not indicate whether the corrosive effects result in the electrochemical removal of tool material or in an
91
increasing susceptibility of the tool to mechanical action due to the removal of part of the tool, e.g. the binder material. In either case, tool or process design to minimize cutter wear will require a knowledge of the factors that control the rate of electrochemical action taking place in the cutting zone. Three of these factors which appear to be important are the materials used in the tool, the chemistry of the wood as represented by the pII and the relative areas of the tool components exposed to electrochemical action. Although the potential developed between the different metals in an electrolyte does not determine the corrosion rate, it does indicate the corrosion susceptibility of the materials. The difference between the WC-Co potential and the WC-Ni potential shows that, from the viewpoint of decreasing electrochemical action, nickel should be a better cemented carbide tool binder than cobalt. The large potential developed between tungsten carbide and iron indicates that, from a corrosion resistance viewpoint, iron is not a suitable cemented carbide binder. The development of cemented carbide tool materials using nickel-based binders is at present under way. The performance of these tools in actual cutting situations in which the electrochemical, mechanical and thermal properties of the tool will determine the total wear has not, as yet, been determined. The electrolyte for the proposed electrochemical reaction taking place during cutting is supplied by the wood. Although the composition of this liquid is not controllable in industrial processing operations, an increased knowledge of its effects may help in the specification of tooling for cutting different species of wood. In addition, the chemical modification of the liquid component of wood may prove to be an impor~t way to study electrochemical tool wear mechanisms experimentally. There is contradictory evidence as to the optimum relative percentage of binder and tungsten carbide grain size in cemented carbide tools for wood-cutting applications. Part of this confusion may be due to the effect of the relative surface areas of the binder and carbide grains in determining the rate of elec~ochemic~ action. The effects of the relative percentage of binder and the carbide grain size on the mechanical and thermal properties of the tool compounds this problem. Cemented carbide tool design is a very complex problem but, in applications where one wear mechanism dominates tool life performance, significant advances have been made. It is hoped that improvements similar to those already made in increasing the tool life when mechanical wear mechanisms dominate can be made in tools for use in wood-cutting applications in which corrosion is an active wear mechanism.
Acknowledgment This work was supported in part by the Multi-Metals Division, Vermont American Corporation. This assistance is gratefully acknowledged.
92
References 1 B, E. Klamecki, Electrical effects in wood cutting tool wear, Holz Rok- Werkst., 36 (1978) 107 - 110. 2 E. Kivimaa, Was ist die Abstumpfung der Holzbearbeitungswerkzuege?, Holz RohWerkst., 10 (1952) 425 I 428. 3 A. V. Alekseev, The influence of electrical phenomena which arise in the cutting of wood on the wear of the tool, Drew. Prom., 6 (1957) 15 - 16. 4 W. E. Hillis and W. M. McKenzie, Chemical attack as a factor in the wear of woodworking cutters, For. Prod. J., 14 (1964) 310 - 312. 5 E. Kirbach and S. Chow, Chemical wear of tungsten carbide cutting tools by western redcedar, For. Prod. J., 26 (1976) 44 - 48. 6 G, S. C. Tsai and B. E. Klamecki, Separation of abrasive and electrochemical tool wear mechanisms in wood cutting, Wood Sci., 12 (1980) 236 - 242.
85
1982) 85 - 92
THE SUSCEPTIBILITY WEAR*
OF WOOD-CUTTING
TOOLS
TO CORROSIVE
GANDI D. MOHAN and BARNEY E. KLAMECKI Forest Products Laboratory,
University of California, Richmond,
CA (U.S.A.)
(Received April 6,198l)
Summary
The machining of green (wet) wood results in unique cutting tool problems. The non-homogeneous multicomponent nature of cutting tools and the water and water solubles in the wood result in electrochemical action. Both mechanical and corrosive tool wear mechanisms are thus active in such wood cutting, The relative magnitudes of mechanical and electrochemical effects were determined by analyzing tool life data in terms of simple models of the individual wear mechanisms. It was demonstrated that under conditions conducive to electrochemic~ action the major part of the total wear was due to corrosion. Some of the factors determining the corrosion susceptibility of cemented carbide tools were studied by measuring the electrical potentials developed between tool components in solutions typical of those found in various woods. The results of these tests indicate that electrochemical action can be influenced by changing the tool binder material, the relative percentage of the tool binder material in the tool and the carbide grain size,
1. Introduction
In most rnate~~-cutting operations, several tool wear mechanisms act simultaneously. Total tool wear is the result of the combined actions and interactions of all the active wear mechanisms. A unique tool wear situation arises in the cutting of green (undried) wood. In these operations the workpiece is composed of the wood substance, water and water solubles characteristic of the tree species. In contrast with mew-cutting operations where the use of an engineered cutting fluid should improve the tool performance, in wood cutting the liquid component of the wood is uncontrollable: its
*Paper presented at the International Conference on Wear of Materials 1981, San Francisco, CA, U.S.A., March 30 - April 1, 1981. 0043-1648/81j0000~0000/$02.50
@ Elsevier Sequoia~~nted
in The Netherlands
86
effect on tool life may be beneficial or detrimental. There is evidence that the liquid component in wood and the non-homogeneous nature of cutting tools give rise to electrochemical effects in the work--chip-tool contact region [l] . The extent of these electrochemical effects, the factors controlling them and their effect on cutting tool wear are the subjects of this paper. Cutting tool life tests and electrochemical test cell results were analyzed with the intent of determining the corrosion susceptibility of cemented carbide tools used to cut wet wood. The extent of electrochemically induced wear and some of the factors which might control the rate of electrochemical action were studied.
2. Background Perhaps the earliest reported works on electrochemical effects in wood cutting are those of Kivimaa [2] and Alekseev [3] . By applying an electrical potential to the cutting tool, large changes in tool life were produced. Increased or decreased rates of wear resulted, depending on the relative tool-work polarity. Hillis and McKenzie [4] reported etching of steel tools when solutions typical of those in eucalyptus were placed on the tools. Kirbach and Chow [ 51 immersed cemented carbide tools in red cedar solutions and produced scanning electron micrographs which show that the cobalt binder is preferentially removed from the tools. The existence of the action of an electrochemical wear mechanism in cutting green wood is emphasized by Klamecki [l] . Significant decreases in tool wear were produced by electrically insulating the cutting tool from the lathe in turning tool life tests. Although the existence of electrochemical effects in wood-cutting tool wear has been demonstrated, the relative magnitude of these effects compared with mechanical wear mechanisms has been studied only recently [6] . The factors controlling the rate of electrochemical action have not been studied.
3. Magnitude of electrochemical
wear relative to mechanical wear
The results of tool life tests in lathe turning are presented in Fig. 1. The tool life T was defined as the cutting time necessary to cause 45 pm of flank wear on the high speed steel and cemented tungsten carbide tools used. A depth of cut of 2.54 mm and a feed of 0.25 mm rev-l were chosen so that, with the relatively low cutting speeds used, only insignificant changes in the thermal and mechanical environments near the cutting edges were expected. Simple models of mechanical and electrochemical wear mechanisms developed by Tsai and Klamecki [ 61 can be applied to these tool life data. If a mechanical wear mechanism in which the amount of tool wear is directly proportional to the length of tool-work sliding is postulated, and if no changes in the tool-work interactions occur over the cutting speed range
87
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I-
1 IO
I
20
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I
40
I
lllll
100
60
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200
0
I
I
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600
Life (mid
Fig. 1. The results of tool life tests in which water-saturated wood (0), air-dried wood ( X), ponderosa pine (- - -) and incense cedar ( -) were turned using high speed steel and cemented carbide tools.
used, the slope of the log V-log 2’ plot will be unity (V is cutting speed and T is tool life). The cutting of air-dried wood yields this result. When watersaturated wood is cut, the tool life is less dependent on cutting speed. Additional wear mechanisms which are independent of cutting speed are then sought to explain the test results. The amount of tool wear caused by electrochemical action is expected to be dependent on the length of time of tool-work contact and not on the cutting velocity. This interpretation can explain the insensitivity of tool wear to cutting speed changes in cutting incense cedar which is a very acidic wood. That is, in the continuous cutting of acidic woods at relatively low cutting speeds, a large part of the total tool wear is due to electrochemical action between the tool and work material. This is reflected in Fig. 1 by the large value of the slope )71for the tool life tests in cutting wet incense cedar with high speed steel tools and by the differences in tool life when green and air-dried woods are cut.
4. Investigation
of the corrosion susceptibility
of cemented carbide tools
4.1. Proposed mechanism of electrochemical wear The demonstration that, in certain wood-cutting situations, corrosion may account for a large part of the wear of the cutting tool raises several questions. From an applications point of view, perhaps the most important question is which factors control the corrosion susceptibility and corrosion rate of cemented carbide tools used to cut wet wood. The multicomponent natures of the carbide cutting tool and the work material are expected to lead to mechanical and electrochemical actions which result in tool wear. The electrochemical part of the wear is modeled as shown in Fig. 2. It is expected that the tool binder material will be anodic and go into solution with the movement of electrons to the carbide component; this is followed by the discharge of this cathode with the formation of hydrogen gas. An
88 Water
Fig. 2. The electrochemical action proposed to explain the corrosive wear of cemented carbide cutting tools used to machine wet wood.
adequate explanation of this process requires an expression relating the rate of electrochemical action to the characteristics of the tool and work materials, i.e. a description of the tool-work infractions. As a first step in this direction the corrosion susceptib~ities of cemented carbide tool components in conditions approximating wood cutting were determined. When two different metals are joined in an electrolytic solution the potential for corrosion is related to the electrical potential which exists between them. Referring to the model of the wood-cutting operation in Fig. 2, it is expected that the important factors determining corrosion susceptibility are the materials present and their distribution. The material considerations are the hard phase and binder materials in the tool and the pH and chemical composition of the electrolyte supplied by the work material. In addition the relative surface areas of the carbide grams and binder which are related to the grain size and the volume percentage of binder will probably be important. With this rationale an attempt was made to characterize the corrosion susceptibility of cemented carbide tools by measuring the electrical potential developed between the component materials when exposed to electrolyte solutions typical of those found in wood. This was done by suspending specimens of the tool component materials in solutions derived from different woods and measuring the electrical potential developed between the specimen and a standard electrode. For this initial work the effects of changing stress and temperature fields in tools during cutting were not investigated. 4.2. Exp~rirnen~~~ procedure The test specimens were made by gluing tungsten carbide particles and cobalt, nickel and iron powders onto cylindrical stainless steel rods using electrically conducting epoxy. The tungsten carbide particles were of 1.5, 6.5,10 and 25 pm sieve size. The electrolyte solutions were prepared by soaking wood chips in distilled water (0.110 kg of chips per liter) at 65 “C for 24 h. The woods used were white fir, which yielded a solution with a pH of approximately 5.0, California black oak (of pH about 3.7) and incense
89
cedar (of pH about 3.1). Each of the specimens was suspended in a glass electrolytic test cell containing the test solutions, and its potential with respect to a standard graphite electrode was measured over a period of 1 h. 4.3. Resu2ts Figure 3 shows the changes with time of the test electrode potentials (with respect to a standard electrode) of tungsten carbide electrodes made from two sizes of tungsten carbide particles in the three test solutions, The values shown are the average of ten tests. After approximately 30 min there was essentially no change in the measured potentials. The roles of the carbide grain size, the tool component material and the solution characteristics in determining the electrode potential are indicated in Figs. 4 and 5. The potentials presented in these figures are those measured after 30 min of immersion and represent the average of five tests. Figure 4 shows that, at tungsten carbide grain sizes larger than about 6 (urn, the grain size has little effect on the measured potential. The use of 1.5 pm particles resulted in potentials which were much larger than those measured using electrodes made from larger particles. The potential differences measured in the different test solutions shown in Figs. 3 and 4 are closely related to the difference in the pH values of the 100
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Incense Cedar
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White Fir f F
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Fig. 3. The potential between tungsten carbide and graphite electrodes in solutions derived from white fir (F), black oak (0) and incense cedar (I) for two different sizes of tun~ten carbide grains. Fig. 4. The potentials developed between graphite and tungsten carbide electrodes made from carbide particles of varying size in solutions derived from white fii (F), incense cedar (I) and black oak (0).
90
Fig. 5. The test electrode potentials with respect to graphite electrodes for tungsten carbide (W) and binder material (C, cobalt; N, nickel; R, iron) electrodes in solutions of varying pH. The tungsten carbide specimens were made from 1.5 pm grains.
solutions. This is shown, together with the potential differences between the tungsten carbide and possible binder metals, in Fig. 5. The potentials of the test electrodes near a pH of 5 are from measurements made in white fir solutions, those between pH values of 3.5 and 4.0 are from black oak solution tests and those near a pH of 3.0 are from the incense cedar solutions. Solutions with a lower pH resulted in lower measured test electrode potentials (with respect to a standard electrode) and this effect was greater for cobalt and nickel than for tungsten carbide. The difference between the rates of change in potential with pH for the different metals tested means that the difference between the potential of the tungsten carbide and the other metals tested varies with the solution pH. For example the change in the WC-Co potential with decreasing pH is greater than the change in the WC-Ni potential.
5. Discussion There is evidence that, when wet wood is cut, electrochemical factors affect the overall cutting tool wear. In some cases, e.g. the continuous cutting of acidic wood, electrochemical action may account for the major portion of the total tool wear. Tool life cutting tests do not indicate whether the corrosive effects result in the electrochemical removal of tool material or in an
91
increasing susceptibility of the tool to mechanical action due to the removal of part of the tool, e.g. the binder material. In either case, tool or process design to minimize cutter wear will require a knowledge of the factors that control the rate of electrochemical action taking place in the cutting zone. Three of these factors which appear to be important are the materials used in the tool, the chemistry of the wood as represented by the pII and the relative areas of the tool components exposed to electrochemical action. Although the potential developed between the different metals in an electrolyte does not determine the corrosion rate, it does indicate the corrosion susceptibility of the materials. The difference between the WC-Co potential and the WC-Ni potential shows that, from the viewpoint of decreasing electrochemical action, nickel should be a better cemented carbide tool binder than cobalt. The large potential developed between tungsten carbide and iron indicates that, from a corrosion resistance viewpoint, iron is not a suitable cemented carbide binder. The development of cemented carbide tool materials using nickel-based binders is at present under way. The performance of these tools in actual cutting situations in which the electrochemical, mechanical and thermal properties of the tool will determine the total wear has not, as yet, been determined. The electrolyte for the proposed electrochemical reaction taking place during cutting is supplied by the wood. Although the composition of this liquid is not controllable in industrial processing operations, an increased knowledge of its effects may help in the specification of tooling for cutting different species of wood. In addition, the chemical modification of the liquid component of wood may prove to be an impor~t way to study electrochemical tool wear mechanisms experimentally. There is contradictory evidence as to the optimum relative percentage of binder and tungsten carbide grain size in cemented carbide tools for wood-cutting applications. Part of this confusion may be due to the effect of the relative surface areas of the binder and carbide grains in determining the rate of elec~ochemic~ action. The effects of the relative percentage of binder and the carbide grain size on the mechanical and thermal properties of the tool compounds this problem. Cemented carbide tool design is a very complex problem but, in applications where one wear mechanism dominates tool life performance, significant advances have been made. It is hoped that improvements similar to those already made in increasing the tool life when mechanical wear mechanisms dominate can be made in tools for use in wood-cutting applications in which corrosion is an active wear mechanism.
Acknowledgment This work was supported in part by the Multi-Metals Division, Vermont American Corporation. This assistance is gratefully acknowledged.
92
References 1 B, E. Klamecki, Electrical effects in wood cutting tool wear, Holz Rok- Werkst., 36 (1978) 107 - 110. 2 E. Kivimaa, Was ist die Abstumpfung der Holzbearbeitungswerkzuege?, Holz RohWerkst., 10 (1952) 425 I 428. 3 A. V. Alekseev, The influence of electrical phenomena which arise in the cutting of wood on the wear of the tool, Drew. Prom., 6 (1957) 15 - 16. 4 W. E. Hillis and W. M. McKenzie, Chemical attack as a factor in the wear of woodworking cutters, For. Prod. J., 14 (1964) 310 - 312. 5 E. Kirbach and S. Chow, Chemical wear of tungsten carbide cutting tools by western redcedar, For. Prod. J., 26 (1976) 44 - 48. 6 G, S. C. Tsai and B. E. Klamecki, Separation of abrasive and electrochemical tool wear mechanisms in wood cutting, Wood Sci., 12 (1980) 236 - 242.