Microhardness - Revision history

Mjimenez47 at 20:03, 14 June 2025

2025-06-14T20:03:19Z

← Older revision		Revision as of 16:03, 14 June 2025
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	For non-work-hardening (brittle) materials, hardness is equal to three times the yield stress (H = 3σ<sub>y</sub>). Since there is a lot of plastic deformation under the indenter, in work-hardening (ductile) materials yield strain cannot be used. The mean plastic strain under the indenter is described by the following equation:		For non-work-hardening (brittle) materials, hardness is equal to three times the yield stress (H = 3σ<sub>y</sub>). Since there is a lot of plastic deformation under the indenter, in work-hardening (ductile) materials yield strain cannot be used. The mean plastic strain under the indenter is described by the following equation:

	<math> ~~{ε_p}~~ = \frac{d′}{5D} </math>		<math>\varepsilon_p = \frac{d'}{5D}</math>

	where d′ is the diameter at the top of the pileup and D is the diameter of the indenter. For d′/D = 0.375, a reasonable value for indentation, the plastic strain, εp = 0.075. Hence, for work-hardening metals, one should take the flow stress at a plastic strain of 0.375 before multiplying it by 3 for a good correlation with the hardness.		where d′ is the diameter at the top of the pileup and D is the diameter of the indenter. For d′/D = 0.375, a reasonable value for indentation, the plastic strain, εp = 0.075. Hence, for work-hardening metals, one should take the flow stress at a plastic strain of 0.375 before multiplying it by 3 for a good correlation with the hardness.

Dnanji: Dnanji moved page Microhardness Tester to Microhardness

2022-11-09T16:57:30Z

Dnanji moved page Microhardness Tester to Microhardness

← Older revision		Revision as of 12:57, 9 November 2022
(No difference)

Rzhou95 at 03:06, 6 October 2021

2021-10-06T03:06:46Z

← Older revision		Revision as of 23:06, 5 October 2021
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	{\|class="infobox"		{\|class="infobox"
	!style="font-size:135%;text-align:center;" \| LECO Microhardness Tester		!style="font-size:135%;text-align:center;" \| LECO Microhardness Tester [https://sites.gatech.edu/mse-mill/sop/microhardness-tester/ [SOP<nowiki>]</nowiki>]
	\|-		\|-
	\|[[File:Microhardness-052621.png\|center\|300px]]		\|[[File:Microhardness-052621.png\|center\|300px]]

Rzhou95 at 22:21, 11 July 2021

2021-07-11T22:21:46Z

← Older revision		Revision as of 18:21, 11 July 2021
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	where P is the load of gf and L is the length of the major diagonal, in micrometers.		where P is the load of gf and L is the length of the major diagonal, in micrometers.

	~~===~~=== Dwell Time ~~===~~===		=== Dwell Time ===
	The ASTM specification for dwell time is 10 to 15 seconds. The dwell time can be changed to meet a specific requirement. As a general rule, a shorter load time is preferable as it reduces the chances of outside influence (vibration, etc.) on the tester.<ref name=":0" />		The ASTM specification for dwell time is 10 to 15 seconds. The dwell time can be changed to meet a specific requirement. As a general rule, a shorter load time is preferable as it reduces the chances of outside influence (vibration, etc.) on the tester.<ref name=":0" />

	~~===~~=== Distance Between Indentations ~~===~~===		=== Distance Between Indentations ===
	Spacing indentations too close together can cause the test piece to become “work hardened” in that area, resulting in false readings. Be sure to maintain proper spacing between indents, in all directions.		Spacing indentations too close together can cause the test piece to become “work hardened” in that area, resulting in false readings. Be sure to maintain proper spacing between indents, in all directions.

	~~===~~=== Vickers vs. Knoop ~~===~~===		=== Vickers vs. Knoop ===
	The Vickers Hardness test has two significant advantages:		The Vickers Hardness test has two significant advantages:

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	The Knoop Hardness test should only be used for measurement of extremely thin plates and brittle materials that cannot be measured by ordinary Vickers Hardness tests. The geometric shape of Knoop indents does vary with the load used.		The Knoop Hardness test should only be used for measurement of extremely thin plates and brittle materials that cannot be measured by ordinary Vickers Hardness tests. The geometric shape of Knoop indents does vary with the load used.

	~~===~~=== Micro-hardness vs. Macro-hardness ~~===~~===		=== Micro-hardness vs. Macro-hardness ===
	There are several problems with the extrapolation of micro-indentation testing to macro indentation results. First, almost invariably, the micro-hardness of any material is higher than its standard macro-hardness. Additionally, the micro-hardness varies with load. Second, there is a tendency for the micro-hardness to increase (up to a few grams); then the hardness value drops with load. At very low loads, one is essentially measuring the hardness of a single grain; the indenter ‘‘sees” a single crystal, and the plastic deformation produced by the indentation is contained in this grain. As the load is increased, plastic deformation of adjoining grains is involved, and a truly polycrystalline deformation regimen is achieved. Grain size has a marked effect on the yield strength and work-hardening characteristics of metals. Yet another potential source of error is the work-hardening introduced in the surface by polishing. The effect of crystallographic orientation, when the impression is restricted to a single grain, is of utmost importance. It is well known that both the yield stress and the work-hardening are dependent on the crystallographic orientation of the material.		There are several problems with the extrapolation of micro-indentation testing to macro indentation results. First, almost invariably, the micro-hardness of any material is higher than its standard macro-hardness. Additionally, the micro-hardness varies with load. Second, there is a tendency for the micro-hardness to increase (up to a few grams); then the hardness value drops with load. At very low loads, one is essentially measuring the hardness of a single grain; the indenter ‘‘sees” a single crystal, and the plastic deformation produced by the indentation is contained in this grain. As the load is increased, plastic deformation of adjoining grains is involved, and a truly polycrystalline deformation regimen is achieved. Grain size has a marked effect on the yield strength and work-hardening characteristics of metals. Yet another potential source of error is the work-hardening introduced in the surface by polishing. The effect of crystallographic orientation, when the impression is restricted to a single grain, is of utmost importance. It is well known that both the yield stress and the work-hardening are dependent on the crystallographic orientation of the material.

Akulaksizoglu3: final form

2021-06-09T14:40:18Z

final form

← Older revision		Revision as of 10:40, 9 June 2021
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	\|-		\|-
	\|'''Dwell Time''': 0-20s		\|'''Dwell Time''': 0-20s
			\|-
			\|'''Standard Comformation:''' ASTM E-384, JIS B-7734, ISO 4545 (Knoop), and ISO 6507 (Vickers)
	\|}		\|}

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	# The indenter and anvil should be clean and well seated.		# The indenter and anvil should be clean and well seated.
	# The surface to be tested should be clean, dry, smooth, and free from oxide. A rough-ground surface is usually adequate for a Vickers ~~macrohardness~~ test, while the Knoop indenter requires ~~prepolishing~~ of the surface to a microscopic grade.		# The surface to be tested should be clean, dry, smooth, and free from oxide. A rough-ground surface is usually adequate for a Vickers macro-hardness test, while the Knoop indenter requires pre-polishing of the surface to a microscopic grade.
	# The surface should be flat and perpendicular to the indenter.		# The surface should be flat and perpendicular to the indenter. Any specimen movement during indentation can cause deformed indents.
	# The thickness of the specimen should be such that a mark or bulge is not produced on the reverse side of the piece. It is recommended that the thickness be at least 10 times the depth of the indentation. Tests should be made on only a single thickness of material.		# The thickness of the specimen should be such that a mark or bulge is not produced on the reverse side of the piece. It is recommended that the thickness be at least 10 times the depth of the indentation. Tests should be made on only a single thickness of material.
	# The spacing between indentations should be at least 3 times the longest dimension of the indentation, to avoid interaction between the work-hardening regions.		# The spacing between indentations should be at least 3 times the longest dimension of the indentation, to avoid interaction between the work-hardening regions.

	== ~~Macroindentation~~ Tests ==		== Macro-indentation Tests ==

	[[File:Hardness1.png\|thumb\|600px\|Diagram of Rockwell Test]]		[[File:Hardness1.png\|thumb\|600px\|Diagram of Rockwell Test]]
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	where P is the applied load (in kgf), d is the average length of the diagonals (in mm), and α is the angle between the opposite faces of the indenter (136°). Conversion to MPa is accomplished by multiplying this value by 9.81. After the indentation, both diagonals of impression are measured, and their average is taken. If the surface is cylindrical or spherical, a correction factor (ASTM Standard E92, Tables 4 through 6) has to be introduced. Microhardness tests utilize a load lighter than 200 gf, and very minute impressions are thus formed; a load of 200 gf produces an indentation of about 50 μm for a medium-hardness metal. These tests are ideally suited to investigate changes in hardness at the microscopic scale. One can measure the hardness of a second-phase particle and identify regions within a grain where differences in hardness occur. Micro-hardness tests are also used to perform routine tests on very small precision components, such as parts of watches. When a metal is alloyed, the distribution of the solute is not even throughout the grain, due to the stress fields produced by the solute atom. The solute atoms often tend to segregate at the grain boundaries, significantly increasing or decreasing the hardness in these areas. This effect can be noted at extremely low concentrations of solute (a few parts per million).		where P is the applied load (in kgf), d is the average length of the diagonals (in mm), and α is the angle between the opposite faces of the indenter (136°). Conversion to MPa is accomplished by multiplying this value by 9.81. After the indentation, both diagonals of impression are measured, and their average is taken. If the surface is cylindrical or spherical, a correction factor (ASTM Standard E92, Tables 4 through 6) has to be introduced. Microhardness tests utilize a load lighter than 200 gf, and very minute impressions are thus formed; a load of 200 gf produces an indentation of about 50 μm for a medium-hardness metal. These tests are ideally suited to investigate changes in hardness at the microscopic scale. One can measure the hardness of a second-phase particle and identify regions within a grain where differences in hardness occur. Micro-hardness tests are also used to perform routine tests on very small precision components, such as parts of watches. When a metal is alloyed, the distribution of the solute is not even throughout the grain, due to the stress fields produced by the solute atom. The solute atoms often tend to segregate at the grain boundaries, significantly increasing or decreasing the hardness in these areas. This effect can be noted at extremely low concentrations of solute (a few parts per million).

	== ~~Microindentation~~ Tests ==		== Micro-indentation Tests ==
			[[File:Screen Shot 2021-06-09 at 10.18.04 AM.png\|thumb\|539x539px\|Shapes of Vickers (VK) and Knoop (HK) indenters, depth and minimum sample thickness requirements of each indenter.<ref name=":0">LECO Corporation. (2017). ''Lm Series Digital Microindentation Tester Instruction Manual''.</ref>]]
			The two most common micro-indentation tests are the Knoop and Vickers tests. The Knoop indenter is an elongated square pyramid, while Vickers indenter is a regular square pyramid.

	~~[[File~~:~~Knoop.PNG\|thumb\|Diagram of Knoop Indenter]]~~		The hardness is obtained from the surface area of the impression and is given by:

	~~The two most common microindentation tests are the Knoop and Vickers tests. The Knoop indenter is an elongated pyramid.~~		<math> KHN = \frac {14229P}{L^2} </math>

	~~The hardness~~ is ~~obtained from~~ the ~~surface area~~ of ~~the impression~~ and is ~~given by:~~		where P is the load of gf and L is the length of the major diagonal, in micrometers.

	~~<math> KHN~~ = ~~\frac {14~~.~~229P}{L^2}~~ </~~math~~>		====== Dwell Time ======
			The ASTM specification for dwell time is 10 to 15 seconds. The dwell time can be changed to meet a specific requirement. As a general rule, a shorter load time is preferable as it reduces the chances of outside influence (vibration, etc.) on the tester.<ref name=":0" />

	~~where P is~~ the ~~load of kgf and L is the length of the major diagonal~~, in mm.		====== Distance Between Indentations ======
			Spacing indentations too close together can cause the test piece to become “work hardened” in that area, resulting in false readings. Be sure to maintain proper spacing between indents, in all directions.

	====== Vickers vs. Knoop ======		====== Vickers vs. Knoop ======
	The ~~very shallow~~ Knoop ~~impression is helpful in testing~~ thin ~~components, such as electro-deposits or hardened layers, or~~ brittle materials.		The Vickers Hardness test has two significant advantages:

			* Geometrically similar indentations and relatively constant hardness values are obtained, regardless of the loads applied, as long as test specimens are homogeneous.
			* Materials ranging from extremely soft to extremely hard can be tested without changing loads.

			The Knoop Hardness test should only be used for measurement of extremely thin plates and brittle materials that cannot be measured by ordinary Vickers Hardness tests. The geometric shape of Knoop indents does vary with the load used.

			====== Micro-hardness vs. Macro-hardness ======
	There are several problems with the extrapolation of micro-indentation testing to macro indentation results. First, almost invariably, the micro-hardness of any material is higher than its standard macro-hardness. Additionally, the micro-hardness varies with load. Second, there is a tendency for the micro-hardness to increase (up to a few grams); then the hardness value drops with load. At very low loads, one is essentially measuring the hardness of a single grain; the indenter ‘‘sees” a single crystal, and the plastic deformation produced by the indentation is contained in this grain. As the load is increased, plastic deformation of adjoining grains is involved, and a truly polycrystalline deformation regimen is achieved. Grain size has a marked effect on the yield strength and work-hardening characteristics of metals. Yet another potential source of error is the work-hardening introduced in the surface by polishing. The effect of crystallographic orientation, when the impression is restricted to a single grain, is of utmost importance. It is well known that both the yield stress and the work-hardening are dependent on the crystallographic orientation of the material.		There are several problems with the extrapolation of micro-indentation testing to macro indentation results. First, almost invariably, the micro-hardness of any material is higher than its standard macro-hardness. Additionally, the micro-hardness varies with load. Second, there is a tendency for the micro-hardness to increase (up to a few grams); then the hardness value drops with load. At very low loads, one is essentially measuring the hardness of a single grain; the indenter ‘‘sees” a single crystal, and the plastic deformation produced by the indentation is contained in this grain. As the load is increased, plastic deformation of adjoining grains is involved, and a truly polycrystalline deformation regimen is achieved. Grain size has a marked effect on the yield strength and work-hardening characteristics of metals. Yet another potential source of error is the work-hardening introduced in the surface by polishing. The effect of crystallographic orientation, when the impression is restricted to a single grain, is of utmost importance. It is well known that both the yield stress and the work-hardening are dependent on the crystallographic orientation of the material.

Akulaksizoglu3: /* Microindentation Tests */

2021-06-09T14:04:24Z

Microindentation Tests

← Older revision		Revision as of 10:04, 9 June 2021
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	<math>HV = \frac{2P \cdot \mathrm{sin(\alpha/2)}}{d^2} \approx \frac{1.8544P}{d^2}</math>		<math>HV = \frac{2P \cdot \mathrm{sin(\alpha/2)}}{d^2} \approx \frac{1.8544P}{d^2}</math>

	where P is the applied load (in kgf), d is the average length of the diagonals (in mm), and α is the angle between the opposite faces of the indenter (136°). Conversion to MPa is accomplished by multiplying this value by 9.81. After the indentation, both diagonals of impression are measured, and their average is taken. If the surface is cylindrical or spherical, a correction factor (ASTM Standard E92, Tables 4 through 6) has to be introduced. Microhardness tests utilize a load lighter than 200 gf, and very minute impressions are thus formed; a load of 200 gf produces an indentation of about 50 μm for a medium-hardness metal. These tests are ideally suited to investigate changes in hardness at the microscopic scale. One can measure the hardness of a second-phase particle and identify regions within a grain where differences in hardness occur. ~~Microhardness~~ tests are also used to perform routine tests on very small precision components, such as parts of watches. When a metal is alloyed, the distribution of the solute is not even throughout the grain, due to the stress fields produced by the solute atom. The solute atoms often tend to segregate at the grain boundaries, significantly increasing or decreasing the hardness in these areas. This effect can be noted at extremely low concentrations of solute (a few parts per million).		where P is the applied load (in kgf), d is the average length of the diagonals (in mm), and α is the angle between the opposite faces of the indenter (136°). Conversion to MPa is accomplished by multiplying this value by 9.81. After the indentation, both diagonals of impression are measured, and their average is taken. If the surface is cylindrical or spherical, a correction factor (ASTM Standard E92, Tables 4 through 6) has to be introduced. Microhardness tests utilize a load lighter than 200 gf, and very minute impressions are thus formed; a load of 200 gf produces an indentation of about 50 μm for a medium-hardness metal. These tests are ideally suited to investigate changes in hardness at the microscopic scale. One can measure the hardness of a second-phase particle and identify regions within a grain where differences in hardness occur. Micro-hardness tests are also used to perform routine tests on very small precision components, such as parts of watches. When a metal is alloyed, the distribution of the solute is not even throughout the grain, due to the stress fields produced by the solute atom. The solute atoms often tend to segregate at the grain boundaries, significantly increasing or decreasing the hardness in these areas. This effect can be noted at extremely low concentrations of solute (a few parts per million).

	== Microindentation Tests ==		== Microindentation Tests ==
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	The hardness is obtained from the surface area of the impression and is given by:		The hardness is obtained from the surface area of the impression and is given by:

	<math> KHN = \frac {14.~~228P~~}{L^2} </math>		<math> KHN = \frac {14.229P}{L^2} </math>

	where P is the load of kgf and L is the length of the major diagonal, in mm. The very shallow Knoop impression is also helpful in testing thin components, such as electrodeposits or hardened layers, or brittle materials. The Vickers microhardness test uses the same 136° pyramid with loads of a few grams.		where P is the load of kgf and L is the length of the major diagonal, in mm.

	There are several problems with the extrapolation of ~~microindentation~~ testing to macro indentation results. First, almost invariably, the ~~microhardness~~ of any material is higher		====== Vickers vs. Knoop ======
	than its standard ~~macrohardness~~. Additionally, the ~~microhardness~~ varies with load. Second, there is a tendency for the ~~microhardness~~ to increase (up to a few grams); then the hardness value drops with load. At very low loads, one is essentially measuring the hardness of a single grain; the indenter ‘‘sees” a single crystal, and the plastic deformation produced by the indentation is contained in this grain. As the load is increased, plastic deformation of adjoining grains is involved, and a truly polycrystalline deformation regimen is achieved. Grain size has a marked effect on the yield strength and work-hardening characteristics of metals. Yet another potential source of error is the work-hardening introduced in the surface by polishing. The effect of crystallographic orientation, when the impression is restricted to a single grain, is of utmost importance. It is well known that both the yield stress and the work-hardening are dependent on the crystallographic orientation of the material.		The very shallow Knoop impression is helpful in testing thin components, such as electro-deposits or hardened layers, or brittle materials.

			There are several problems with the extrapolation of micro-indentation testing to macro indentation results. First, almost invariably, the micro-hardness of any material is higher than its standard macro-hardness. Additionally, the micro-hardness varies with load. Second, there is a tendency for the micro-hardness to increase (up to a few grams); then the hardness value drops with load. At very low loads, one is essentially measuring the hardness of a single grain; the indenter ‘‘sees” a single crystal, and the plastic deformation produced by the indentation is contained in this grain. As the load is increased, plastic deformation of adjoining grains is involved, and a truly polycrystalline deformation regimen is achieved. Grain size has a marked effect on the yield strength and work-hardening characteristics of metals. Yet another potential source of error is the work-hardening introduced in the surface by polishing. The effect of crystallographic orientation, when the impression is restricted to a single grain, is of utmost importance. It is well known that both the yield stress and the work-hardening are dependent on the crystallographic orientation of the material.

	== Relationships Between Yield Stress and Hardness ==		== Relationships Between Yield Stress and Hardness ==
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	where d′ is the diameter at the top of the pileup and D is the diameter of the indenter. For d′/D = 0.375, a reasonable value for indentation, the plastic strain, εp = 0.075. Hence, for work-hardening metals, one should take the flow stress at a plastic strain of 0.375 before multiplying it by 3 for a good correlation with the hardness.		where d′ is the diameter at the top of the pileup and D is the diameter of the indenter. For d′/D = 0.375, a reasonable value for indentation, the plastic strain, εp = 0.075. Hence, for work-hardening metals, one should take the flow stress at a plastic strain of 0.375 before multiplying it by 3 for a good correlation with the hardness.


	== Converting Between Scales ==		== Converting Between Scales ==
	If the desired hardness scale cannot be measured by the Leco tester, a conversion table such as [https://pgisteel.com/hardness-conversion-chart/ this]<ref name="Conversion"> ''Hardness Conversion Chart''. PGI Steel. (n.d.). https://pgisteel.com/hardness-conversion-chart/ </ref>. may be used to find the value on the desired scale. It should be noted that not all hardness scales cover the same range or are designed for the same materials.		If the desired hardness scale cannot be measured by the Leco tester, a conversion table such as [https://pgisteel.com/hardness-conversion-chart/ this]<ref name="Conversion"> ''Hardness Conversion Chart''. PGI Steel. (n.d.). https://pgisteel.com/hardness-conversion-chart/ </ref>. may be used to find the value on the desired scale. It should be noted that not all hardness scales cover the same range or are designed for the same materials.

Amarin32 at 17:25, 7 June 2021

2021-06-07T17:25:46Z

← Older revision		Revision as of 13:25, 7 June 2021
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	\|-		\|-
	\|'''Indenters''': Vickers, Knoop		\|'''Indenters''': Vickers, Knoop
			\|-
			\|'''Load Force''': 5-2000gf (0.05-19.61N)
			\|-
			\|'''Dwell Time''': 0-20s
	\|}		\|}

Amarin32 at 17:20, 7 June 2021

2021-06-07T17:20:41Z

← Older revision		Revision as of 13:20, 7 June 2021
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	== Converting Between Scales ==		== Converting Between Scales ==
	If the desired hardness scale cannot be measured by the Leco tester, a conversion table such as [https://pgisteel.com/hardness-conversion-chart/ this]<ref ~~Name:~~"Conversion" ''Hardness Conversion Chart''. PGI Steel. (n.d.). ~~<nowiki>~~https://pgisteel.com/hardness-conversion-chart/~~</nowiki>~~ </ref>. may be used to find the value on the desired scale. It should be noted that not all hardness scales cover the same range or are designed for the same materials.		If the desired hardness scale cannot be measured by the Leco tester, a conversion table such as [https://pgisteel.com/hardness-conversion-chart/ this]<ref name="Conversion"> ''Hardness Conversion Chart''. PGI Steel. (n.d.). https://pgisteel.com/hardness-conversion-chart/ </ref>. may be used to find the value on the desired scale. It should be noted that not all hardness scales cover the same range or are designed for the same materials.

	== References ==		== References ==

Amarin32 at 17:19, 7 June 2021

2021-06-07T17:19:21Z

← Older revision		Revision as of 13:19, 7 June 2021
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	== Preparation ==		== Preparation ==

	The following precautions are recommended for reproducible results in hardness testing:<ref>		The following precautions are recommended for reproducible results in hardness testing:<ref name="NEWAGE"> NEWAGE Hardness Testers. (n.d.). Hardness Testing Basics. NEWAGE Hardness Testers - Rockwell Testers, Brinell Testers, Microhardness Testers, Optical Systems and Hardness Testing Software. https://www.hardnesstesters.com/test-types/hardness-testing-basics. </ref>

	# The indenter and anvil should be clean and well seated.		# The indenter and anvil should be clean and well seated.
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	== Converting Between Scales ==		== Converting Between Scales ==
	If the desired hardness scale cannot be measured by the Leco tester, a conversion table such as [https://pgisteel.com/hardness-conversion-chart/ this]<ref> may be used to find the value on the desired scale. It should be noted that not all hardness scales cover the same range or are designed for the same materials.		If the desired hardness scale cannot be measured by the Leco tester, a conversion table such as [https://pgisteel.com/hardness-conversion-chart/ this]<ref Name:"Conversion" ''Hardness Conversion Chart''. PGI Steel. (n.d.). <nowiki>https://pgisteel.com/hardness-conversion-chart/</nowiki> </ref>. may be used to find the value on the desired scale. It should be noted that not all hardness scales cover the same range or are designed for the same materials.

	== References ==		== References ==
	<references />		<references />

	[2] NEWAGE Hardness Testers. (n.d.). Hardness Testing Basics. NEWAGE Hardness Testers - Rockwell Testers, Brinell Testers, Microhardness Testers, Optical Systems and Hardness Testing Software. https://www.hardnesstesters.com/test-types/hardness-testing-basics.

	~~[3] ''Hardness Conversion Chart''. PGI Steel. (n.d.). <nowiki>https://pgisteel.com/hardness-conversion-chart/</nowiki>.~~

	[[Category:Equipment\|meas]]		[[Category:Equipment\|meas]]

Rzhou95 at 16:44, 7 June 2021

2021-06-07T16:44:26Z

← Older revision		Revision as of 12:44, 7 June 2021
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	\|}		\|}

	The LECO LM 248 AT is a hardness tester that is designed to measure the hardness of materials on the microscopic level. ~~The~~ machine can magnify a surface as much as 50x and measure the hardness of a sample on the Vickers, Knoop, and Rockwell C scales. Hardness testing is used for two general characterizations: material characteristics (such as confirming material, testing hardenability, and predicting tensile strength) or functionality (testing wear resistance, toughness, and resistance to impact).		The LECO LM 248 AT is a hardness tester that is designed to measure the hardness of materials on the microscopic level. The machine can magnify a surface as much as 50x and measure the hardness of a sample on the Vickers, Knoop, and Rockwell C scales. Hardness testing is used for two general characterizations: material characteristics (such as confirming material, testing hardenability, and predicting tensile strength) or functionality (testing wear resistance, toughness, and resistance to impact).

	== Introduction ==		== Introduction ==

	Hardness tests are a simple method to determine the resistance of a metal to plastic deformation. <ref>Meyers, M., & Chawla, K. (2016). Hardness. In Mechanical Behavior of Materials (2nd ed., pp. 214–225). chapter, Cambridge University Press.</ref> Indentation tests constitute the vast majority of hardness tests and can be divided into three classes: nanoindentation, microindentation, and macroindentation (based on the indentation load used). The smaller the indentation, the harder the material. Both the yield stress and the work-hardening characteristics of the metal are important in determining the hardness. Hardness is not considered a fundamental property of a material; it represents a quantity measure on an arbitrary scale. There are several different methods used for hardness testing, which use varying shapes of indenters and loads. The MILL’s Leco LM 248AT comes with Vickers and Knoop indenters and calculates Rockwell C hardness from whichever of these scales is being used.		Hardness tests are a simple method to determine the resistance of a metal to plastic deformation.<ref name="Meyers">Meyers, M., & Chawla, K. (2016). Hardness. In Mechanical Behavior of Materials (2nd ed., pp. 214–225). chapter, Cambridge University Press.</ref> Indentation tests constitute the vast majority of hardness tests and can be divided into three classes: nanoindentation, microindentation, and macroindentation (based on the indentation load used). The smaller the indentation, the harder the material. Both the yield stress and the work-hardening characteristics of the metal are important in determining the hardness. Hardness is not considered a fundamental property of a material; it represents a quantity measure on an arbitrary scale. There are several different methods used for hardness testing, which use varying shapes of indenters and loads. The MILL’s Leco LM 248AT comes with Vickers and Knoop indenters and calculates Rockwell C hardness from whichever of these scales is being used.

	== Preparation ==		== Preparation ==