JPH11352061A - Method for analyzing surface layer by emission spectrochemical analysis - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and accurately measure a surface layer, for example, the depth of a decarburized layer, the thickness of a coat, etc., by measuring the intensity of the emitted light of a specific wavelength continuously by an emission spectrochemical analysis, and comparing the relationship between the elapsed time of a discharge time and an element concentration corresponding to the measured intensity with a relationship between a cut depth and a discharge time obtained beforehand. SOLUTION: High energy discharging is conducted for a predetermined time to the surface of an iron steel sample 1 consisting essentially of the same chemical component as a sample, and a relationship between a cut depth H and a discharge time is obtained. Since the surface cut by the discharge is largest at a part immediately below an electrode 2, and an emission intensity is largest at the part, the cut depth H is measured at the part immediately below the electrode 2. A light emitted from the sample with a known carbon concentration as a result of the discharging is divided by a spectroscope 3, thereby obtaining a spectral emission intensity. The carbon concentration is related to the detected intensity. The relationship between the discharge time and the cut depth H, and a relation formula between the detected intensity and the carbon concentration are set to an analyzer. While the sample to be analyzed is subjected to predetermined high-energy discharging under the same conditions, the detected intensity is measured for each predetermined time unit, so that the carbon concentration is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for easily analyzing the distribution state of a specific element on a surface layer such as a decarburized layer or a modified film formed on a steel sample by emission spectroscopy.

[0002]

2. Description of the Related Art Decarburization of the surface layer is inevitable for steel materials which have been processed at a high temperature such as hot rolling, hot forging or heat treatment. The decarburized surface has a reduced carbon concentration and thus becomes a quenched and softened state, and does not have a predetermined hardness even when subjected to a heat treatment, resulting in reduced fatigue strength and poor wear resistance. Therefore, when treating steel at high temperatures, care is taken to minimize decarburization.

In order to improve the wear resistance and corrosion resistance of machine parts, a carburized layer or the like is formed on the surface of the machine parts by carburizing or carbonitriding, or a modified coating is formed on the surface of the machine parts. Is performed. The amount of carbon to be introduced and the composition and thickness of the film differ depending on the required mechanical properties, and it is very important whether the amount of carbon and the thickness of the film are as required.

[0004] Therefore, it is necessary to analyze the sample to determine whether the depth of the decarburized layer formed on the product surface, the gradient of the amount of carbon, the film thickness, the concentration distribution of the main elements in the film, and the like are as required. Checking has been done conventionally.

In general, emission spectroscopy is used for analyzing the composition of steel (about φ5 mm, depth 5 μm) such as the analysis of carburized layers. When analyzing the depth of the decarburized layer using this emission spectroscopy method, the thickness of the sample is measured in advance with a micrometer, and the carbon concentration on the surface at that thickness is measured by emission spectroscopy. Then, the surface is ground to a predetermined thickness with a surface grinder or the like, and the carbon concentration of the ground surface is again determined.
Determined by emission spectroscopy. This is repeated until the desired depth is reached. The analyzed depth is determined from the difference in sample thickness before and after grinding.

[0006] From a plurality of measured values obtained stepwise as described above, a carbon amount transition curve in the depth direction is obtained, and the depth of the decarburized layer is identified. In the emission spectroscopy method, the surface of the sample is excited by a discharge between the steel sample and the counter electrode to emit light, and this is spectrally separated by a spectroscope to obtain a wavelength of a target specific element (carbon or the like). The qualitative and quantitative analysis of each element is performed by measuring the intensity of the spectral line. And conventionally, the discharge energy is not so high and the discharge time is short.

There are many methods for measuring the film thickness of the film constituting the surface layer of a product, and a typical measuring method is a measuring method using fluorescent X-rays (JISH8501-1988). In this measuring method, the intensity of fluorescent X-rays generated by irradiating a coating sample with X-rays is detected, and the intensity is converted into the thickness of the coating to obtain the intensity.

[0008]

However, in the analysis of the depth of the decarburized layer by the above-mentioned conventional emission spectroscopy,
Before analyzing each ground surface (each depth position), pre-processing (grinding etc.) must be performed before analyzing each ground surface (each depth position) in order to analyze the ground surface at each stage while grinding the surface several times step by step to the target depth. ) Is not only required, but only analytical information separated for each grinding thickness can be obtained, and a continuous concentration distribution in the depth direction cannot be obtained.

[0009] This also has the problem that the resolution depends on the thickness of one grinding, so that it is not possible to secure the resolution in the depth direction with a sample having an extremely thin layer, and analysis cannot be performed. Further, in the method of measuring a film by the fluorescent X-ray, if the film is too thick, measurement becomes impossible. Usually, the limit of the thickness of this method is about 10 μm.

[0010] For a sample having a relatively thick metal film, there is no technique for measuring the composition and film thickness of the film by a simple method. The present invention has been made by paying attention to the above problems, and a surface layer analysis by emission spectroscopy for accurately measuring a surface layer such as a depth of a decarburized layer and a film thickness of a film by a simple method. It is an object to provide a method.

[0011]

Means for Solving the Problems To solve the above problems, the surface analysis method according to the present invention employs an emission spectroscopy, which comprises the steps of forming a layer such as a decarburized layer or a carburized layer formed on the surface of a sample made of a steel material and modifying the surface. A surface layer analysis method for analyzing the concentration distribution of a specific element in a film such as a porous film by emission spectroscopy, and continuously performing a predetermined high-energy discharge on a sample surface made of a steel material similar to the sample to be analyzed. The relationship between the shaving depth of the sample surface at the time of discharge and the discharge time is determined in advance, and the emission intensity of a specific wavelength is continuously measured by emission spectroscopy while discharging the sample to be analyzed using the predetermined high-energy discharge. Then, the relationship between the elapsed time of the discharge time and the element concentration corresponding to the measured emission intensity, and the relationship between the previously obtained shaving depth and the discharge time, formed on the sample surface. Or it is characterized in analyzing the film.

The energy capacity of the high-energy discharge / discharge has only to be large enough to gradually cut the sample surface.
And, in case of deep quantification, large energy capacity is set.
What is necessary is just to set energy capacity small.

The amount of surface abrasion per unit time due to high energy discharge differs depending on the steel material, the depth of the abrasion, and the like. By determining the relationship between the surface shaving depth and the discharge time for a sample made of a steel material, the discharge time and the shaving depth, that is, the depth position from the sample surface to be analyzed, correspond one-to-one with the discharge time. Attached.

Here, the discharge time and the shaving depth may be determined once, and a predetermined calibration curve may be obtained. Thereafter, calibration may be appropriately performed. The concentration of the element to be analyzed, such as the carbon concentration in the sample, does not significantly affect the relationship between the discharge time and the shaving depth, and is determined mainly by the main matrix of the steel material.

Then, the target element concentration is continuously measured in the depth direction by performing discharge for a predetermined time by high-energy discharge and performing continuous emission spectroscopy, and the decarburization depth, It is possible to determine the film thickness and the like.

That is, without the need for pretreatment such as grinding,
With one discharge, a continuous concentration distribution in the depth direction for the specific element is obtained.

[0017]

Next, a first embodiment of the present invention will be described with reference to the drawings. In the following description, it is assumed that a sample in which a decarburized layer is formed on a surface layer is to be analyzed.

As shown in FIG. 1, a high-energy discharge was performed for a predetermined time on the surface of a steel sample 1 having the same main chemical components as the target sample under the same conditions as the emission spectroscopy described later. The relationship between the shaving depth H of the surface and the discharge time is determined. Here, each one-dot chain line shown in FIG. 1 indicates the state of the ground surface (milling surface) cut by the discharge when a predetermined discharge time has elapsed.

The above relationship is obtained by measuring the shaving depth H at that time in a predetermined discharge time unit using a dial gauge or the like, and associating the discharge time with the shaving depth. In the cutting of the surface by electric discharge, the portion directly below the electrode 2 is cut most, but taking into consideration that the emission intensity from that portion is the largest, the electrode 2
Is defined as the scraping depth H.

The relationship between the scraping depth H and the discharge time obtained above is obtained, for example, as a relationship of a curve as shown in FIG. This means that the amount removed (evaporated amount) per unit discharge time is not constant as it is removed,
This is because saturation occurs at a predetermined depth. In FIG.
This is an example of saturation at about 1 mm.

Further, as the above-mentioned sample 1, a plurality of samples of known carbon concentration (known standard samples having a uniform carbon concentration up to the core) consisting of several levels of carbon concentration are used, and for each of the known samples, light emission by discharge is emitted. By spectroscopy with the spectroscope 3, specifying the carbon spectrum by wavelength, and obtaining the emission intensity (detection intensity) of the spectrum, the carbon concentration and the detection intensity are related. The relationship between the detected intensity and the carbon concentration is almost linearly proportional. However, the relationship between the detection intensity and the carbon concentration may use existing data.

As described above, the relationship between the discharge time and the shaving depth H, and the detection intensity (the emission intensity of the specific wavelength spectrum)
And the carbon concentration are determined, and these relational expressions are set in advance in the analyzer or a computer connected to the analyzer.

Then, the detection intensity of the sample to be analyzed is continuously measured at predetermined time units (for example, every one second) while discharging at a predetermined high energy discharge under the same conditions as above, and the discharge time is measured. The shaving depth H, that is, the depth from the surface, is determined from the elapsed time, and the carbon concentration at the depth is determined from the intensity detected at a predetermined elapsed time of the discharge time.

Thus, a continuous carbon concentration distribution from the surface to the depth direction is obtained, and the depth of the decarburized layer is obtained from a position where the gradient of the carbon concentration is saturated by a predetermined amount. As described above, in the present embodiment, unlike the analysis of the surface layer by the conventional emission spectroscopy, it is possible to obtain a continuous carbon concentration distribution in the depth direction by one continuous discharge. It is possible to analyze the surface layer easily in a short time and with high accuracy.

Further, since the concentration distribution of the specific element which is continuous in the depth direction can be obtained, the following analysis of the surface layer can be performed. Defects such as segregation can be correctly determined.

Since the state of interface diffusion of the coating element to the substrate in the surface modified film or the like is continuously detected, the film forming strength can be determined. For example, as the element of the main component of the film continuously diffuses in the depth direction and gradually changes, the film thickness is determined to be higher.

Here, in the above embodiment, only the distribution of the carbon concentration is measured in one discharge, but in one discharge,
You may set so that the density | concentration of two or more types of specific elements may be measured.

The high energy capacity at the time of the discharge may be set according to the target depth of the layer. Next, an example in which a modified film is formed on the surface layer will be described. In addition, about the member etc. similar to the said embodiment, the same code | symbol is used and the description is abbreviate | omitted.

Here, as shown in FIG. 3, if the saturation depth that can be cut by high-energy discharge is equal to or greater than the film thickness t, the film 1a
And the light emission intensity of the substrate 1b (underlying film) can be detected.

As in the first embodiment, the relationship between the discharge time and the shaving depth H is determined in advance and set in the analyzer. Then, the relationship between the detection intensity (the emission intensity of the wavelength spectrum of the main element of the coating film) and the discharge time (the scraping depth H) is obtained.

At this time, as shown in FIG. 4, the detection intensity decreases as the abrasion depth H increases, so that the thickness t of the film 1a is determined from the variation of the emission intensity. be able to.

That is, the position A where the detection intensity is saturated may be determined as the thickness of the film 1a. Since the element to be measured is also diffused in the substrate 1b, the predetermined saturated state is set in the film 1a.
Is set at the boundary between the object and the substrate 1b.

Further, for the same type of film, the above analysis is performed on several types of samples whose film thickness t is known in advance, and the relationship between the film thickness t and the detected intensity K when the detected intensity is saturated is obtained. Thus, the relationship between the film thickness t and the detection intensity K at the time of saturation is obtained in advance. The relationship between the film thickness t and the detection intensity K at the time of saturation has a first-order proportional relationship as described later.

Then, with respect to the target sample 1, the detection intensity K when the detection intensity is saturated by continuous discharge with the high energy discharge for a predetermined time is obtained, and the film thickness t and the detection intensity K at the time of saturation are obtained. Is determined from the relationship.

In this case, it is only necessary to determine the presence or absence of saturation based on the change in the detected intensity per unit time, and it is not necessary to use the discharge time.

[0036]

[First Embodiment] First, a first embodiment of the present invention in a case where a decarburized layer is formed on a surface layer will be described.

Table 1 shows the main chemical components of the test pieces used in Example 1 (sample 1 has a disk test piece of φ60 mm × 8 mm).

[0038]

[Table 1]

First, two kinds of high carbon chromium steels shown in Table 1 (S
UJ2) test piece, high energy capacity (10μ)
(F × 1000 V), the experiment was performed for the maximum shaving depth, and the result shown in FIG. 2 was obtained.

In the existing emission spectrometer, since the capacity of the capacitor is 10 μF and the voltage is about 1000 V, the maximum value of the high energy capacity (10 μF)
X 1000 V), but the energy capacity can be set higher by preparing a device capable of outputting a higher energy capacity.

As can be seen from FIG. 2, when the discharge is performed for about 60 seconds, the shaving depth H is saturated and the shaving depth H is cut by about 0.1 mm at the maximum. That is, in this case, the maximum is 0.1 m
It can be seen that decarburized layers up to m can be analyzed.

The analysis conditions were as follows: discharge was continuously performed at an energy capacity of 10 μF × 1000 V, and the relationship between the detection intensity and the element concentration, the discharge time (analysis time) and the shaving depth were determined in advance in the same manner as in the above embodiment. The relationship with the height H is determined and set in the analyzer.

Then, the actual sample (decarburized sample)
Was used to determine the relationship between the detection intensity (element concentration) and the discharge time (depth from the surface) by the method described in the above embodiment, and the result shown in FIG. 5 was obtained.

In FIG. 5, the solid line is the measurement result. The circles and dashed lines are the results measured by the conventional measurement method for comparison. The conventional measurement method is to measure the thickness in advance with a micrometer, analyze the surface with emission spectroscopy, then grind the analysis surface to the desired depth with a surface grinder, and use the emission spectroscopy for the ground surface. analyse. By repeating this, analysis is performed up to the target depth. The depth of the measurement surface is calculated from the difference between the thickness of the sample before and after the grinding.

As can be seen from FIG. 5, even the simple method based on the present invention has the same measurement accuracy as the conventional measurement method. [Second Embodiment] Next,
Second embodiment of the present invention in the case where the surface layer is formed of a modified film
An example will be described. This embodiment relates to a case where a modified film is formed on a surface layer.

First, as the test pieces used in the experiment, test pieces having five kinds of thickness each of a chromium film and a nickel film were prepared. Specimens were prepared in advance by JIS microscopy (JISH
8501-1988). Table 2 shows the results.

[0047]

[Table 2]

Next, two kinds of high carbon chromium steel (matrix mainly Fe) shown in Table 1 and sample No. 5 (chrome coating 8
0 μm) and sample 1 NO. 10 (nickel coating 82 μm)
An experiment was performed on the discharge time and the maximum shaving depth using the test piece of m).

The analysis conditions are as shown in Table 3 below.

[0050]

[Table 3]

FIG. 6 shows the measurement results of the discharge time and the scraping depth H. This means that for each metal, high energy,
It was performed with three types of energy capacity, arc light and normal discharge.

As can be seen from FIG. 6, the higher the energy capacity of iron, chromium, and nickel, the deeper the metal was cut.

Prior to the actual measurement, a standard sample having a known thickness (the chrome film-treated products No. 1 to NO. 4 and the nickel film-treated products No. 6 to NO. 9) was used to carry out the above-described measurement. As described in the embodiment, the relationship between the main component (Cr or Ni) of the film thickness and the detection intensity at the time of saturation was obtained. The results are shown in FIGS.

Next, with respect to the sample whose thickness is unknown, the detection intensity is continuously obtained by discharging with a high energy discharge for a predetermined time, and the film thickness corresponding to the value at which the detection intensity is saturated is calculated as shown in FIG.
Alternatively, it was obtained using FIG.

The results are shown in the upper part of Table 4.

[0056]

[Table 4]

For confirmation, when the film thickness of the same film thickness unknown sample was determined with a JIS microscope, the same thickness was obtained as shown in the lower part of Table 4 above. From this, it is understood that the film thickness can be accurately obtained even in the film thickness measurement based on the present invention.

[0058]

As described above, when the surface analysis method based on the emission spectroscopy according to the present invention is employed, the depth and thickness of the decarburized layer can be easily and accurately obtained by only one continuous discharge. The surface layer such as the surface layer can be analyzed.

In addition, despite its simplicity, it is possible to obtain a concentration distribution (concentration gradient) continuous for a specific element in the depth direction.

[Brief description of the drawings]

FIG. 1 is a diagram showing a shaving depth by high-energy discharge according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a discharge time and a shaving depth according to the embodiment of the present invention.

FIG. 3 is a diagram showing a state of light emission intensity when a modified film is present on a surface layer.

FIG. 4 is a diagram showing a relationship between a film thickness and a detection intensity.

FIG. 5 is a diagram showing analysis results of carbon concentration distribution of a decarburized layer by a high energy discharge and a conventional method.

6A and 6B are diagrams showing the relationship between the discharge capacity and the shaving depth of each element, where FIG. 6A shows the case of iron, FIG. 6B shows the case of chromium, and FIG. 6C shows the case of nickel.

FIG. 7 is a diagram showing a relationship between a detection intensity and a film thickness of a chromium film at the time of saturation.

FIG. 8 is a diagram showing the relationship between the detection intensity and the film thickness of the nickel film at the time of saturation.

[Description of Signs] 1 Sample 2 Electrode H Shaving depth

Claims (1)

[Claims] 1. A surface layer analysis method for analyzing the concentration distribution of a specific element in a layer such as a decarburized layer and a carburized layer formed on the surface of a sample made of a steel material and a film such as a surface modified film by emission spectroscopy. Then, for the sample surface made of the same steel material as the sample to be analyzed, the relationship between the shaving depth of the sample surface and the discharge time when discharging continuously at a predetermined high energy discharge is determined in advance, and the sample to be analyzed is About, measuring the emission intensity of a specific wavelength continuously by emission spectral analysis while discharging with the predetermined high energy discharge, the relationship between the elapsed time of the discharge time and the element concentration corresponding to the measured emission intensity, and A surface analysis method based on emission spectroscopy, wherein a layer or a film formed on a sample surface is analyzed based on a relationship between the shaving depth and a discharge time obtained in advance.