CN117165899A - Method for regulating and controlling thickness of nitrogen supersaturated austenite phase layer in plasma nitrocarburizing process - Google Patents
Method for regulating and controlling thickness of nitrogen supersaturated austenite phase layer in plasma nitrocarburizing process Download PDFInfo
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 100
- 238000000034 method Methods 0.000 title claims abstract description 56
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 51
- 230000001105 regulatory effect Effects 0.000 title claims abstract description 15
- 230000001276 controlling effect Effects 0.000 title claims abstract description 13
- 229910001566 austenite Inorganic materials 0.000 title abstract description 10
- 229910001220 stainless steel Inorganic materials 0.000 claims abstract description 24
- 239000010935 stainless steel Substances 0.000 claims abstract description 24
- 238000009792 diffusion process Methods 0.000 claims abstract description 12
- 238000005121 nitriding Methods 0.000 claims abstract description 11
- 239000011248 coating agent Substances 0.000 claims abstract description 7
- 238000000576 coating method Methods 0.000 claims abstract description 7
- 239000001257 hydrogen Substances 0.000 claims description 39
- 229910052739 hydrogen Inorganic materials 0.000 claims description 39
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 36
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 33
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 30
- 229910052786 argon Inorganic materials 0.000 claims description 15
- 238000002294 plasma sputter deposition Methods 0.000 claims description 8
- 238000004544 sputter deposition Methods 0.000 claims description 7
- 150000002431 hydrogen Chemical class 0.000 claims description 6
- 238000004140 cleaning Methods 0.000 claims description 2
- 238000001816 cooling Methods 0.000 claims description 2
- 238000005498 polishing Methods 0.000 claims description 2
- 230000007797 corrosion Effects 0.000 abstract description 7
- 238000005260 corrosion Methods 0.000 abstract description 7
- 230000004048 modification Effects 0.000 abstract description 6
- 238000012986 modification Methods 0.000 abstract description 6
- 238000007747 plating Methods 0.000 abstract description 5
- CKUAXEQHGKSLHN-UHFFFAOYSA-N [C].[N] Chemical compound [C].[N] CKUAXEQHGKSLHN-UHFFFAOYSA-N 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 12
- 150000002500 ions Chemical class 0.000 description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 7
- 229910052799 carbon Inorganic materials 0.000 description 7
- 239000011159 matrix material Substances 0.000 description 5
- 125000004433 nitrogen atom Chemical group N* 0.000 description 5
- 230000008595 infiltration Effects 0.000 description 4
- 238000001764 infiltration Methods 0.000 description 4
- 125000004429 atom Chemical group 0.000 description 3
- 238000010835 comparative analysis Methods 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 238000007733 ion plating Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000002161 passivation Methods 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 230000002035 prolonged effect Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 150000001722 carbon compounds Chemical class 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005262 decarbonization Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000005251 gamma ray Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 150000003254 radicals Chemical class 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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Abstract
The invention discloses a method for regulating and controlling the thickness of a nitrogen supersaturated austenite phase layer in a plasma nitrocarburizing process, which comprises the following steps: putting a 316L stainless steel workpiece into a nitriding furnace, performing plasma nitrocarburizing for 6 hours under the condition that the pressure in the furnace is 130Pa, and adjusting the thermodynamic temperature of the cementation, the nitrogen volume ratio and the cathode voltage to gamma of the workpiece N Regulating and controlling the thickness delta of the phase layer; the formula for δ is as follows:wherein T is the thermodynamic temperature of the diffusion coating, c is the volume ratio of nitrogen, U is the cathode voltage of the workpiece, and delta sigma is an error term. The invention adjusts the thermodynamic temperature of the diffusion plating, the volume ratio of nitrogen and the cathode voltage of the workpiece to gamma in the plasma nitrocarburizing process N Thickness of phase layer and gamma N Phase layer thickness is taken up in nitrogen-carbon co-The thickness ratio of the seepage modification layer is regulated and controlled, so that the hardness and pitting corrosion resistance of the surface of the workpiece can be improved.
Description
Technical Field
The invention relates to the technical field of ion plating, in particular to a method for regulating and controlling the thickness of a nitrogen supersaturated austenite phase layer in a plasma nitrocarburizing process.
Background
The coating formed by the ion plating process at low temperature mainly consists of metastable supersaturated phase, and can improve the hardness of the matrix without affecting the tolerance of the matrixErodibility. The metastable supersaturated phase is commonly referred to as the "expanded austenite" or "S" phase, for example: nitrogen supersaturated austenitic phase gamma N Supersaturated austenitic phase gamma of carbon C . In the FCC (face centered cubic) lattice of austenite, interstitial nitrogen atoms and carbon atoms are solid-dissolved in octahedral interstitial sites in the cell center. Gamma ray N Phase layer and gamma C The phase layers, although structurally similar, have a larger lattice expansion than C associated with N, gamma N Phase layer is compared with gamma C The phase layer produces greater expansion and higher density of dislocations in the crystal planes, thus gamma N Phase layer and gamma C The phase layer has a higher hardness than the phase layer. In addition, when pitting occurs in the passivation film on the surface of stainless steel, gamma N The solid-dissolved nitrogen atoms on the surface of the phase can be released in the corrosion process, and H in the pit can be consumed + Formation of NH 4+ Thereby inhibiting the growth of pitting corrosion, thus gamma N Phase layer and gamma C The phase layer also has better pitting corrosion resistance.
Therefore, a method capable of regulating and controlling gamma in the process of Plasma Nitrocarburizing (PNC) is developed N The method of the thickness of the phase layer has very important significance.
Disclosure of Invention
The invention aims to provide a method for regulating and controlling the thickness of a nitrogen supersaturated austenitic phase layer in a plasma nitrocarburizing process.
The technical scheme adopted by the invention is as follows:
the method for regulating and controlling the thickness of the nitrogen supersaturated austenite phase layer in the plasma nitrocarburizing process comprises the following steps:
putting a 316L stainless steel workpiece into a nitriding furnace, performing plasma nitrocarburizing for 6 hours under the condition that the pressure in the furnace is 130Pa, and adjusting the thermodynamic temperature of the cementation, the nitrogen volume ratio and the cathode voltage to gamma of the workpiece N Regulating and controlling the thickness delta of the phase layer; the delta is calculated as follows:
wherein T is the thermodynamic temperature of the diffusion plating (in K), c is the volume ratio of nitrogen (expressed by a small number, for example, 63% is expressed as 0.63), U is the cathode voltage of the workpiece (in V), and (+/-delta sigma) is an error term.
Preferably, the specific operation of the plasma nitrocarburizing is as follows:
1) Hydrogen pretreatment: placing a 316L stainless steel workpiece in a nitriding furnace, vacuumizing, introducing hydrogen, and performing hydrogen plasma sputtering on the surface of the workpiece;
2) First stage low temperature plasma nitrocarburizing: introducing methane, nitrogen, hydrogen and argon into a nitriding furnace, and performing plasma nitrocarburizing on the workpiece treated in the step 1);
3) Second stage low temperature plasma nitrocarburizing: introducing methane, nitrogen and hydrogen into a nitriding furnace, performing plasma nitrocarburizing on the workpiece treated in the step 2), and cooling to room temperature along with the furnace.
Preferably, the work piece of step 1) is overpolished and cleaned before being subjected to hydrogen plasma sputtering.
Preferably, the specific operation of the vacuumizing in the step 1) is as follows: vacuumizing until the pressure in the furnace is 7 Pa-8 Pa.
Preferably, the operating parameters of the hydrogen plasma sputtering in step 1) are: the flow rate of hydrogen is 180 mL/min-220 mL/min, the pressure in the furnace is kept at 60 Pa-80 Pa, the voltage of the workpiece cathode is 580V-600V, the temperature in the furnace is 280-320 ℃, and the sputtering time is 50-70 min. The 316L stainless steel workpiece surface is bombarded by hydrogen plasma, so that on one hand, an oxide film on the workpiece surface can be effectively removed, the obstruction of the oxide film to active atoms penetrating into a matrix in a nitrocarburizing process is reduced, on the other hand, the diameter of hydrogen molecules is smaller compared with that of argon molecules, the energy obtained in the process of the diffusion plating is lower than that of the argon molecules, the sputtering loss of the matrix is small when the workpiece is bombarded, and the influence on the corrosion resistance of the workpiece is reduced. The sputtering time is controlled to be 50-70 min to effectively remove the passivation film on the surface of the workpiece as much as possible and keep the active state of the surface of the workpiece, but if the sputtering time is too long, the cost is high.
Preferably, the operating parameters of the plasma nitrocarburizing in step 2) are: the flow rate of methane is 100-200 mL/min, the flow rate of nitrogen is 400-600 mL/min, the flow rate of hydrogen is 200-250 mL/min, the flow rate of argon is 40-60 mL/min, the pressure in the furnace is kept at 130Pa, the voltage of a workpiece connected with a cathode is 630-880V, the temperature in the furnace is 380-450 ℃, and the time of plasma nitrocarburizing is 25-35 min. Meanwhile, hydrogen and argon are introduced as permeation assisting gases, nitrogen can be influenced by stress induced on the surface of the substrate by the hydrogen, and the driving force of nitrogen diffusion is increased, so that the nitrogen is permeated deeper, and the higher nitrogen concentration generated by the existence of the hydrogen further allows carbon to diffuse deeper into the substrate, so that a 316L stainless steel workpiece can obtain a thicker nitrocarburizing modified layer. The concentration of high-energy particles in the ion body can be improved in a short time due to the existence of argon, but the concentration should be controlled between 25min and 35min so as to prevent the defect on the surface of the workpiece from increasing due to the strong sputtering action of the argon, thereby affecting the performance of the workpiece.
Preferably, the operating parameters of the plasma nitrocarburizing in step 3) are: the flow rate of methane is 100 mL/min-200 mL/min, the flow rate of nitrogen is 500 mL/min-600 mL/min, the pressure in the furnace is kept at 130Pa, the voltage of the workpiece connected with the cathode is 630V-880V, the temperature in the furnace is 380-450 ℃, and the time of plasma nitrocarburizing is 265-275 min. Stopping introducing argon and increasing the introducing amount of hydrogen, wherein the hydrogen-containing gas mixture reacts with carbon on the surface of the 316L stainless steel workpiece to form CH 3 Free radical, thereby realizing decarbonization, ensuring that nitrogen atoms can continuously permeate into the matrix, and increasing the nitrogen-rich layer gamma in the modified layer N Thickness of the phase layer.
Preferably, the methane flow rate in step 2) and step 3) is the same.
Preferably, the nitrogen flow rates in step 2) and step 3) are the same.
Preferably, the thickness of the nitrocarburizing modification layer formed by the first-stage low-temperature plasma nitrocarburizing in the step 2) and the second-stage low-temperature plasma nitrocarburizing in the step 3) is more than 20 μm. The total time of plasma nitrocarburizing is controlled to be 6 hours, a nitrocarburizing modified layer with the thickness of more than 20 mu m can be obtained, along with the increase of the thickness of the nitrocarburizing modified layer, the path of active nitrogen atom penetrating into the matrix is prolonged, the infiltration rate is slowed down along with the prolonged time of plasma nitrocarburizing, the excessive time of plasma nitrocarburizing can cause phase change and compound precipitation, the cost is higher, and the infiltration effect is poor.
The beneficial effects of the invention are as follows: the invention adjusts the thermodynamic temperature of the diffusion plating, the volume ratio of nitrogen and the cathode voltage of the workpiece to gamma in the plasma nitrocarburizing process N Thickness of phase layer and gamma N The thickness of the phase layer accounts for the thickness of the nitrocarburizing modification layer to be regulated and controlled, so that the hardness and pitting corrosion resistance of the surface of the workpiece can be improved.
Specifically:
1) The invention obtains the thermodynamic temperature of the diffusion plating, the nitrogen volume ratio, the cathode voltage of the workpiece and the gamma in the plasma nitrocarburizing process N Nonlinear functional relationship between phase layer thicknesses δ=f (T, c, U), γ can be adjusted by adjusting process parameters in the functional equation N The thickness of the phase layer has good process stability, easy control and low preparation cost;
2) The invention utilizes the discharge state of the permeation assisting gas hydrogen and argon in the plasma nitrocarburizing process to play a role in assisting the permeation of nitrogen atoms by adjusting the adding time of the permeation assisting gas hydrogen and argon, the gas combination and the proportion between the hydrogen and the argon, and utilizes the N in the plasma in the nitrocarburizing process 2+ Proper hydrogen and argon flow rates and heat preservation time are selected according to the dissociation degree of the nitrogen-carrying ions and the carbon-based molecules to improve gamma N Thickness of phase layer and gamma N The phase layer thickness accounts for the proportion of the thickness of the nitrocarburizing modified layer, so that the hardness and pitting corrosion resistance of the surface of the workpiece are improved;
3) The invention uses hydrogen as main permeation assisting gas, and adjusts the gas volume ratio by adjusting the hydrogen flow to keep the total air pressure in the nitriding furnace unchanged and changing the methane and nitrogen flow, thereby adjusting gamma N The thickness of the phase layer (nitrogen-rich layer) and the carbon compound (Fe) in the nitrocarburizing modification layer caused by too high carbon potential is avoided by adjusting the ratio of methane gas 3 C) Precipitation affects the surface properties of the workpiece.
Drawings
Fig. 1 is a metallographic cross-sectional view of the A, B, C, D, E and F group 316L stainless steel workpieces of example 1.
Fig. 2 is an XRD pattern of the A, B, C, D, E and F group 316L stainless steel workpieces in example 1.
Fig. 3 is a plot of delta=f (T, c, U) function fits in example 1.
Fig. 4 is a metallographic cross-sectional view of the G, H, I and J group 316L stainless steel workpieces of example 2.
Fig. 5 is a plot of delta=f (T, c, U) function fit in example 2.
Fig. 6 is a metallographic cross-sectional view of K, L, M and N groups of 316L stainless steel workpieces in example 3.
Fig. 7 is a plot of delta=f (T, c, U) function fits in example 3.
Detailed Description
The invention is further illustrated and described below in connection with specific examples.
Example 1:
a method for regulating and controlling the thickness of a nitrogen supersaturated austenite phase layer in a plasma nitrocarburizing process comprises the steps of carrying out grouping experiments by setting different experimental conditions, changing the volume ratio of methane and nitrogen in a permeated gas, keeping the total air pressure in a furnace unchanged by adjusting the flow of hydrogen, and verifying gamma N The phase layer thickness delta has nonlinear functional relation with the thermodynamic temperature of the diffusion coating, the nitrogen volume ratio and the cathode voltage of the workpiece, and specifically comprises the following steps:
1) Hydrogen pretreatment: polishing and cleaning a 316L stainless steel workpiece (the chemical components of the 316L stainless steel are shown in table 1), placing the workpiece on a cathode plate of a PN-IV type multifunctional glow ion nitriding furnace, vacuumizing to 7.6Pa, introducing hydrogen, and performing hydrogen plasma sputtering on the surface of the workpiece, wherein the operation parameters of the hydrogen plasma sputtering are as follows: the hydrogen flow is 200mL/min, the pressure in the furnace is kept at 70Pa, the voltage of the workpiece connected with the cathode is 600V, the temperature in the furnace is 300 ℃, and the sputtering time is 60min;
TABLE 1 chemical composition of 316L stainless steel
2) First stage low temperature plasma nitrocarburizing (methane and nitrogen flow and volume ratio c% are shown in table 2): using N 2 +CH 4 +H 2 +Ar ion nitrocarburizing process with N 2 As nitrogen source, by CH 4 As the carbon source, H is selected 2 And Ar component mixed gas is used as permeation assisting gas to carry out plasma nitrocarburizing on the workpiece treated in the step 1), and the operation parameters of the plasma nitrocarburizing are as follows: the flow rate of methane is 100-200 mL/min, the flow rate of nitrogen is 400-600 mL/min, the flow rate of hydrogen is 200-250 mL/min, the flow rate of argon is 50mL/min, the pressure in the furnace is kept at 130Pa, the voltage of a workpiece cathode is 730V, the temperature in the furnace is 450 ℃, and the time of plasma nitrocarburizing is 30min;
3) Second stage low temperature plasma nitrocarburizing (flow and volume ratio c% of nitrogen and methane are shown in table 2): using N 2 +CH 4 +H 2 Ion nitrocarburizing process with N 2 As nitrogen source, by CH 4 As the carbon source, H is selected 2 The workpiece treated in the step 2) is subjected to plasma nitrocarburizing as an infiltration assisting gas, and the operation parameters of the plasma nitrocarburizing are as follows: the flow rate of methane is 100-200 mL/min, the flow rate of nitrogen is 400-600 mL/min, the flow rate of hydrogen is regulated to keep the pressure in the furnace at 130Pa, the voltage of the workpiece connected with the cathode is 730V, the temperature in the furnace is 450 ℃, the time of plasma nitrocarburizing is 330min, and then the furnace is cooled to the room temperature.
TABLE 2 flow and volume fractions of methane and Nitrogen c%
Experimental comparative analysis:
1) Metallographic cross-sectional views of the A, B, C, D, E and F group 316L stainless steel workpieces in this example are shown in FIG. 1.
As can be seen from fig. 1: A. b, C, D, E and F group 316L stainless Steel workpiece gamma N The phase layers were 10.0 μm, 8.4 μm, 6.3 μm, 5.8 μm, 4.2 μm and 3.7 μm thick in this orderm。
2) The X-ray diffraction (XRD) patterns of the A, B, C, D, E and F group 316L stainless steel workpieces in this example are shown in fig. 2.
As can be seen from fig. 2: A. b, C, D, E and F group 316L stainless Steel workpiece gamma NC (111) The larger the interstitial atom content in the expanded austenite, the larger the lattice distortion, the larger the peak shift, the phase peak positions are 41.187 degrees, 41.314 degrees, 41.627 degrees, 41.702 degrees, 41.732 degrees and 42.618 degrees respectively; the group A infiltration layer has the largest interstitial atom content, and gamma in the nitrocarburizing modification layer N The proportion of phase layers is higher, which is consistent with the metallographic cross-section.
It can be seen that gamma N The thickness delta of the phase layer is in nonlinear function relation with the thermodynamic temperature of the diffusion coating, the volume ratio of nitrogen and the cathode voltage of the workpiece, namelyIn this embodiment, t=723.15k, u=730V, time is 6h, and air pressure is 130Pa, i.e. the functional relation δ=f (T, c, U) can be simplified as δ=f (c) = 56.417c 3.922 Delta sigma was substituted into c (c is 0.63, 0.61, 0.60, 0.57, 0.52 and 0.47) corresponding to experimental groups A, B, C, D, E and F of this example, delta calculations were 9.19 μm, 8.11 μm, 7.60 μm, 6.22 μm, 4.34 μm and 2.92 μm (delta=f (T, c, U) function fitting graphs are shown in fig. 3), and the average error term was about 0.52 μm compared to metallographic test results.
In conclusion, gamma N The phase layer thickness delta is compared with a semi-empirical formula of nitrogen ratio process parameter delta=f (T, c, U) to accord with experimental results.
Example 2:
a method for controlling the thickness of a nitrogen supersaturated austenite phase layer in a plasma nitrocarburizing process, and other process parameters, process steps and materials except for temperature are the same as in example 1 (the ion nitrocarburizing process parameters are shown in table 3).
TABLE 3 parameters of ion nitrocarburizing process
Experimental comparative analysis:
metallographic cross-sectional views of the G, H, I and J group 316L stainless steel workpieces in this example are shown in FIG. 4.
As can be seen from fig. 4: G. h, I and J group 316L stainless Steel workpiece gamma N The phase layers were 10.0 μm, 7.9 μm, 5.8 μm and 3.2 μm thick in this order.
It can be seen that gamma N The thickness delta of the phase layer is in nonlinear function relation with the thermodynamic temperature of the diffusion coating, the volume ratio of nitrogen and the cathode voltage of the workpiece, namelyIn this embodiment, c=0.63, u=730V, the time is 6h, the air pressure is 130Pa, i.e. the functional relation δ=f (T, c, U) can be simplified asSubstituting T corresponding to experimental groups G, H, I and J of this example (T723.15K, 693.15K, 673.15K, and 653.15K, respectively), delta calculations were 9.55 μm, 7.15 μm, 5.85 μm, and 4.73 μm (delta=f (T, c, U) function fitting graph is shown in fig. 5), and the average error term was about 0.61 μm compared to the metallographic test results.
In conclusion, gamma N The phase layer thickness delta is matched with the semi-empirical formula of the temperature process parameter delta=f (T, c, U) according to the experimental result.
Example 3:
a method for controlling the thickness of a nitrogen supersaturated austenitic phase layer in a plasma nitrocarburizing process, and other process parameters, process steps and materials except for voltage are the same as in example 1 (the ion nitrocarburizing process parameters are shown in table 4).
TABLE 4 ion nitrocarburizing process parameters
Experimental comparative analysis:
a metallographic cross-sectional view of K, L, M and N groups of 316L stainless steel workpieces in this example is shown in fig. 6.
As can be seen from fig. 6: G. h, I and J group 316L stainless Steel workpiece gamma N The phase layers were 11.0 μm, 10.0 μm, 7.9 μm and 3.7 μm in this order.
It can be seen that gamma N The thickness delta of the phase layer is in nonlinear function relation with the thermodynamic temperature of the diffusion coating, the volume ratio of nitrogen and the cathode voltage of the workpiece, namelyIn this embodiment, c=0.63, t= 693.15K, the time is 6h, the air pressure is 130Pa, i.e. the functional relation δ=f (T, c, U) can be simplified as δ=f (c) = 5.077 × (0.00158U) 2.4 The values of delta sigma are substituted into the U corresponding to experimental groups G, H, I and J of this example (U: 880V, 830V, 730V, and 630V, respectively), and the delta calculations are 11.19 μm, 9.7 μm, 7.1 μm, and 4.92 μm (delta=f (T, c, U) function fitting graph is shown in fig. 7), with an average error term of about 0.71 μm compared to the metallographic test results.
In conclusion, gamma N The phase layer thickness delta is matched with the semi-empirical formula of the voltage process parameter delta=f (T, c, U) according to the experimental result.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (10)
1. A method for regulating the thickness of a nitrogen supersaturated austenitic phase layer in a plasma nitrocarburizing process, comprising the steps of: putting a 316L stainless steel workpiece into a nitriding furnace, performing plasma nitrocarburizing for 6 hours under the condition that the pressure in the furnace is 130Pa, and adjusting the thermodynamic temperature of the cementation, the nitrogen volume ratio and the cathode voltage to gamma of the workpiece N Regulating and controlling the thickness delta of the phase layer; the delta is calculated as follows:
wherein T is the thermodynamic temperature of the diffusion coating, c is the volume ratio of nitrogen, U is the cathode voltage of the workpiece, and delta sigma is an error term.
2. The method according to claim 1, characterized in that: the specific operation of the plasma nitrocarburizing is as follows:
1) Hydrogen pretreatment: placing a 316L stainless steel workpiece in a nitriding furnace, vacuumizing, introducing hydrogen, and performing hydrogen plasma sputtering on the surface of the workpiece;
2) First stage low temperature plasma nitrocarburizing: introducing methane, nitrogen, hydrogen and argon into a nitriding furnace, and performing plasma nitrocarburizing on the workpiece treated in the step 1);
3) Second stage low temperature plasma nitrocarburizing: introducing methane, nitrogen and hydrogen into a nitriding furnace, performing plasma nitrocarburizing on the workpiece treated in the step 2), and cooling to room temperature along with the furnace.
3. The method according to claim 2, characterized in that: the operating parameters of the hydrogen plasma sputtering in the step 1) are as follows: the flow rate of hydrogen is 180 mL/min-220 mL/min, the pressure in the furnace is kept at 60 Pa-80 Pa, the voltage of the workpiece cathode is 580V-600V, the temperature in the furnace is 280-320 ℃, and the sputtering time is 50-70 min.
4. The method according to claim 2, characterized in that: the operation parameters of the plasma nitrocarburizing are as follows: the flow rate of methane is 100-200 mL/min, the flow rate of nitrogen is 400-600 mL/min, the flow rate of hydrogen is 200-250 mL/min, the flow rate of argon is 40-60 mL/min, the pressure in the furnace is kept at 130Pa, the voltage of a workpiece connected with a cathode is 630-880V, the temperature in the furnace is 380-450 ℃, and the time of plasma nitrocarburizing is 25-35 min.
5. The method according to claim 2, characterized in that: the operation parameters of the plasma nitrocarburizing are as follows: the flow rate of methane is 100 mL/min-200 mL/min, the flow rate of nitrogen is 500 mL/min-600 mL/min, the pressure in the furnace is kept at 130Pa, the voltage of the workpiece connected with the cathode is 630V-880V, the temperature in the furnace is 380-450 ℃, and the time of plasma nitrocarburizing is 265-275 min.
6. The method according to any one of claims 2 to 5, characterized in that: step 1) the workpiece is subjected to over-polishing and cleaning before being subjected to hydrogen plasma sputtering.
7. The method according to any one of claims 2 to 5, characterized in that: the specific operation of the vacuumizing in the step 1) is as follows: vacuumizing until the pressure in the furnace is 7 Pa-8 Pa.
8. The method according to any one of claims 2 to 5, characterized in that: the methane flow rates in step 2) and step 3) are the same.
9. The method according to any one of claims 2 to 5, characterized in that: the nitrogen flow rates in step 2) and step 3) are the same.
10. The method according to any one of claims 2 to 5, characterized in that: the thickness of the nitrocarburizing modified layer formed by the first section of low-temperature plasma nitrocarburizing in the step 2) and the second section of low-temperature plasma nitrocarburizing in the step 3) is more than 20 mu m.
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