Heat treatment processing technology for high-toughness gear

Abstract

The invention provides a heat treatment machining process for a high-toughness gear. The heat treatment machining process comprises the following steps: selecting CPM 10V high-speed steel as a pre-selected material, carrying out two times of normalizing forging on the pre-selected material to obtain a grain-refined pre-selected material, carrying out quenching and tempering heat treatment on the pre-selected material to obtain a material blank with the core hardness of 31-45HRC, carrying out semi-finish machining on the material blank, and carrying out heat treatment on the material blank to obtain the high-toughness gear. The semi-finish machining gear part has the following beneficial effects that the high-performance powder metallurgy high-speed steel with extremely high pertinence serves as a substrate, the grain refinement forging technology is overlaid, the congenital advantages that the powder metallurgy high-speed steel is uniform in component and excellent in bending strength and impact toughness are reserved, grains are refined through forging, and the mechanical property of the gear part is improved. The internal structure of the material is more uniform and compact, a firm foundation is built for performance improvement of subsequent heat treatment, and performance limitation caused by a single material or a single pretreatment process is avoided.

Description

Technical Field

[0001] This invention is a heat treatment process for high-strength and tough gears, belonging to the field of metal heat treatment technology. Background Technology

[0002] As a core component of transmission systems, gears are widely used in high-end equipment such as aero engines, gas turbines, and rotary kilns. Their performance directly determines the overall operational stability, reliability, and service life of the machine. The working environment of such equipment often involves high speed, high load, strong impact, and intense friction, which places stringent comprehensive performance requirements on gears. They need to have excellent toughness and fatigue resistance in the core, high hardness and wear resistance on the surface, and ensure dimensional accuracy and long-term operational stability.

[0003] There are still many problems to be solved in the existing materials and heat treatment processes related to gear manufacturing. Traditional cast high-strength and tough gears have inherent defects such as macroscopic segregation of alloying elements and coarse carbide particles, resulting in poor material performance balance and difficulty in long-term stable operation under conditions of strong impact and high friction. Therefore, a new process is needed to solve this problem. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a heat treatment process for high-strength and tough gears, thereby solving the inherent defects of traditional cast high-strength and tough gears mentioned in the background, such as macroscopic segregation of alloy elements and coarse carbide particles, which lead to poor material performance balance and difficulty in long-term stable operation under conditions of strong impact and high friction.

[0005] To achieve the above objectives, the present invention provides a high-strength and tough gear heat treatment process, comprising the following steps: S1. Select high-speed steel of type CPM 10V as the pre-selected material, perform two normalizing forgings on the pre-selected material to obtain a pre-selected material with refined grains, and perform quenching and tempering heat treatment on the pre-selected material to obtain a material billet with a core hardness of 31-45HRC. S2. Perform semi-precision machining on the material blank to obtain a semi-precision machined gear component; S3. Stabilize the semi-precision machined gear components to eliminate internal stress and homogenize the structure; S4. The surface of the semi-finished gear component to be nitrided is subjected to sandblasting treatment to activate the material surface; S5. Nitriding heat treatment is performed on the semi-finished gear parts after sandblasting to obtain the first gear; S6. Perform stage quenching treatment on the first gear to obtain the second gear; S7. Perform surface carburizing and isothermal quenching on the second gear to obtain the third gear; S8. Preset the scanning range, scanning step size, and scanning speed; acquire X-ray diffraction patterns, neutron diffraction data, and eddy current signals on the surface of the third gear; extract features from the X-ray diffraction patterns, neutron diffraction data, and eddy current signals to obtain X-ray diffraction features, neutron diffraction features, and eddy current features; and concatenate the X-ray diffraction features, neutron diffraction features, and eddy current features to obtain a feature vector. S9. Using the feature vector as input to the parameter prediction model, the tempering temperature and tempering time are obtained. The third gear is subjected to isothermal tempering treatment based on the tempering temperature and tempering time to obtain the fourth gear. S10. The fourth gear is strengthened by a multi-energy field coupling stress relief process to obtain the fifth gear; S11. Collect the tooth profile data of the fifth gear, and perform precision machining on the fifth gear through a deformation compensation cutting strategy to obtain a high-strength and tough gear.

[0006] Further, in step S1, the pre-selected material with refined grains is held at 850-1200℃ for 150-210 min to transform the microstructure into austenitic microstructure. It is then quenched in quenching oil at 45-85℃ to transform the austenitic microstructure into martensite and granular carbides. After quenching, it is oil-cooled within 1 hour and then tempered 2-3 times at 550-750℃ to homogenize the martensite microstructure.

[0007] Further, in step S5, the nitriding heat treatment involves placing the semi-finished gear component in an ammonia atmosphere and heating it to 500-550℃ for 5-8 hours, during which the ammonia decomposition rate is 37-54%. The nitriding heat treatment employs a two-stage nitriding process. The temperature of the first stage nitriding process is 530-570℃, and the nitrogen potential is 0.35%-0.45%. The temperature of the second stage nitriding process is 550-600℃, and the nitrogen potential is 0.35%-0.45%.

[0008] Further, in step S6, the first gear is placed in a quenching furnace, and the furnace temperature is raised to 900℃ at a rate of 15-20℃ / min and held for 1.5-2 hours. After the holding period, it is transferred to a quenching tank containing polymer quenching liquid within 40 seconds. The flow rate of the circulating pump is adjusted to 600-800L / min to make the cooling rate 90-120℃ / s. When the temperature drops to 500-550℃, it is transferred to a quenching tank containing water-based coolant within 35 seconds. The flow rate of the circulating pump is adjusted to 450-500L / min to make the cooling rate 25-45℃ / s until the temperature drops to 190-210℃, thus obtaining the second gear.

[0009] Further, in step S7, the second gear is placed in a carburizing furnace and heated to 950-970°C at a rate of 10-15°C / min, and then carburized for 4-5 hours. The carbon content in the carburizing furnace is 1.0%-1.2%. After the carburizing is completed, the gear is transferred to an isothermal quenching furnace at 330-360°C within 40 seconds for isothermal salt bath treatment and held for 2 hours. After the holding is completed, the gear is removed and allowed to cool naturally to room temperature to obtain the third gear.

[0010] Further, in step S8, the position of each diffraction peak, the intensity value corresponding to the highest point, and the full width at half maximum (FWHM) are extracted from the X-ray diffraction pattern. The peak intensity ratio of adjacent diffraction peaks is calculated, the grain size is calculated using the Scherrer formula, and the residual stress corresponding to different azimuth angles is calculated. The peak intensity ratio, grain size, and residual stress are then combined as X-ray diffraction features. The method for obtaining neutron diffraction features includes: extracting the diffraction peak displacements of preset crystal planes at different depths from the neutron diffraction data, calculating the lattice strain, calculating the internal stress according to Hooke's law, and combining the lattice strain and internal stress as neutron diffraction features. The method for obtaining eddy current features includes: acquiring the current in the eddy current signal and the current corresponding to the phase and amplitude changes, calculating the crack depth and crack size, and combining the crack depth and crack size as eddy current features.

[0011] The beneficial effects of this invention are as follows: By using highly targeted high-performance powder metallurgy high-speed steel as the base and superimposing a grain refinement forging process, it not only retains the inherent advantages of powder metallurgy high-speed steel such as uniform composition, excellent bending strength and impact toughness, but also refines the grains through forging, making the internal structure of the material more uniform and dense, laying a solid foundation for the performance improvement of subsequent heat treatment, and avoiding the performance limitations caused by a single material or a single pretreatment process.

[0012] Precise heat treatment ensures the core of the gear core meets the requirements of impact resistance and fatigue resistance. Gradient quenching and surface carburizing treatment achieve a balance between surface strength and core toughness. Finally, sandblasting activation and segmented nitriding processes are used to maximize surface wear resistance, allowing the gear to exhibit excellent performance in different stress areas.

[0013] Through the synergistic effect of various technological advantages, gears have achieved a qualitative improvement in key indicators such as fatigue life, impact resistance, and wear resistance reliability. They can not only withstand complex working conditions such as high speed, high load, and strong impact, but also maintain stable performance over a long period of time, reducing equipment maintenance frequency and operating costs. Detailed Implementation

[0014] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0015] This invention provides a technical solution: a heat treatment process for high-strength and tough gears, comprising the following steps: S1. Select high-speed steel of type CPM 10V as the pre-selected material, perform two normalizing forgings on the pre-selected material to obtain a pre-selected material with refined grains, and perform quenching and tempering heat treatment on the pre-selected material to obtain a material billet with a core hardness of 31-45HRC. S2. Perform semi-finish machining on the material blank to obtain semi-finished gear components; S3. Stabilize semi-precision machined gear components to eliminate internal stress and homogenize the structure; S4. The surface of the semi-finished gear parts to be nitrided is sandblasted to activate the material surface; S5. Nitriding heat treatment is performed on the semi-finished gear parts after sandblasting to obtain the first gear; S6. Perform stage quenching treatment on the first gear to obtain the second gear; S7. Perform surface carburizing and isothermal quenching on the second gear to obtain the third gear; S8. Preset the scanning range, scanning step size, and scanning speed; acquire X-ray diffraction patterns, neutron diffraction data, and eddy current signals on the surface of the third gear; extract features from the X-ray diffraction patterns, neutron diffraction data, and eddy current signals to obtain X-ray diffraction features, neutron diffraction features, and eddy current features; and stitch together the X-ray diffraction features, neutron diffraction features, and eddy current features to obtain a feature vector. S9. Use the feature vector as input to the parameter prediction model to obtain the tempering temperature and tempering time. Perform isothermal tempering on the third gear according to the tempering temperature and tempering time to obtain the fourth gear. S10. The fourth gear is strengthened by a multi-energy field coupling stress relief process to obtain the fifth gear; S11. Collect the tooth profile data of the fifth gear, and perform precision machining on the fifth gear through a deformation compensation cutting strategy to obtain a high-strength and tough gear.

[0016] In step S1, the pre-selected material for grain refinement is held at 850-1200℃ for 150-210 min to transform the microstructure into austenitic microstructure. It is then quenched in quenching oil at 45-85℃ to transform the austenitic microstructure into martensite and granular carbides. After quenching, it is oil-cooled within 1 hour and then tempered 2-3 times at 550-750℃ to homogenize the martensite microstructure.

[0017] In step S5, the semi-finished gear parts are placed in an ammonia atmosphere and heated to 500-550℃ for 5-8 hours. During the heating process, the ammonia decomposition rate is 37-54%. The nitriding heat treatment adopts a two-stage nitriding process. The temperature of the first stage nitriding process is 530-570℃, and the nitrogen potential is 0.35%-0.45%. The temperature of the second stage nitriding process is 550-600℃, and the nitrogen potential is 0.35%-0.45%.

[0018] In step S6, the first gear is placed in a quenching furnace, and the furnace temperature is raised to 900℃ at a rate of 15-20℃ / min and held for 1.5-2 hours. After the holding period, it is transferred to a quenching tank containing polymer quenching liquid within 40 seconds. The flow rate of the circulating pump is adjusted to 600-800L / min to make the cooling rate 90-120℃ / s. When the temperature drops to 500-550℃, it is transferred to a quenching tank containing water-based coolant within 35 seconds. The flow rate of the circulating pump is adjusted to 450-500L / min to make the cooling rate 25-45℃ / s until the temperature drops to 190-210℃, thus obtaining the second gear.

[0019] In step S7, the second gear is placed in a carburizing furnace and heated to 950-970℃ at a rate of 10-15℃ / min, and then carburized for 4-5 hours. The carbon content in the carburizing furnace is 1.0%-1.2%. After the carburizing is completed, the gear is transferred to an isothermal quenching furnace at 330-360℃ within 40 seconds for isothermal salt bath treatment and held for 2 hours. After the holding is completed, the gear is removed and allowed to cool naturally to room temperature to obtain the third gear.

[0020] In step S8, the position of each diffraction peak, the intensity value corresponding to the highest point, and the full width at half maximum (FWHM) are extracted from the X-ray diffraction pattern. The peak intensity ratio of adjacent diffraction peaks is calculated, the grain size is calculated using the Scherrer formula, and the residual stress corresponding to different azimuth angles is calculated. The peak intensity ratio, grain size, and residual stress are then combined as X-ray diffraction features. The method for obtaining neutron diffraction features includes: extracting the diffraction peak displacements of preset crystal planes at different depths from the neutron diffraction data, calculating the lattice strain, calculating the internal stress according to Hooke's law, and combining the lattice strain and internal stress as neutron diffraction features. The method for obtaining eddy current features includes: acquiring the current in the eddy current signal and the current corresponding to the changes in phase and amplitude, calculating the crack depth and crack size, and combining the crack depth and crack size as eddy current features.

[0021] Example 1: High-speed steel of type CPM 10V was selected as the pre-selected material. The pre-selected material was subjected to two normalizing forging processes to obtain a pre-selected material with refined grains. The pre-selected material was held at 850℃ for 150°C to transform the microstructure into an austenitic microstructure. It was then quenched in quenching oil at 45℃ to transform the austenitic microstructure into a martensite microstructure and granular carbides. It was then oil-cooled within 1 hour after quenching and then tempered twice at 550℃ to homogenize the martensite microstructure. The pre-selected material was then subjected to quenching and tempering heat treatment to obtain a material billet with a core hardness of 31HRC. S2. Perform semi-finish machining on the material blank to obtain semi-finished gear components; S3. Stabilize semi-precision machined gear components to eliminate internal stress and homogenize the structure; S4. The surface of the semi-finished gear parts to be nitrided is sandblasted to activate the material surface; S5. The semi-finished machined gear components after sandblasting are subjected to nitriding heat treatment to obtain the first gear. During nitriding heat treatment, the semi-finished machined gear components are placed in an ammonia atmosphere and heated to 500℃ for 5 hours. The ammonia decomposition rate during the heating process is 37%. The nitriding heat treatment adopts a two-stage nitriding process. The temperature of the first stage nitriding process is 530℃, and the nitrogen potential is 0.35%. The temperature of the second stage nitriding process is 550℃, and the nitrogen potential is 0.35%. S6. Perform staged quenching treatment on the first gear, and place the second gear in a carburizing furnace. Heat the gear to 950°C at a rate of 10°C / min, and hold for 4 hours for carburizing. The carbon content in the carburizing furnace is 1.0%. After the carburizing is completed, transfer the gear to an isothermal quenching furnace at 330°C within 40 seconds for isothermal salt bath treatment and hold for 2 hours. After the holding is completed, remove the gear and allow it to cool naturally to room temperature to obtain the second gear. S7. Perform surface carburizing and isothermal quenching on the second gear to obtain the third gear; S8. Preset the scanning range, scanning step size, and scanning speed; acquire X-ray diffraction patterns, neutron diffraction data, and eddy current signals on the surface of the third gear; extract features from the X-ray diffraction patterns, neutron diffraction data, and eddy current signals to obtain X-ray diffraction features, neutron diffraction features, and eddy current features; stitch the X-ray diffraction features, neutron diffraction features, and eddy current features to obtain a feature vector; place the first gear in a quenching furnace, raise the furnace temperature to 900℃ at a rate of 15℃ / min, and hold it for 1.5h; after holding, transfer it to a quenching tank containing polymer quenching liquid within 40s; adjust the circulation pump flow rate to 600L / min to make the cooling rate 90℃ / s; until the temperature drops to 500℃, transfer it to a quenching tank containing water-based coolant within 35s; adjust the circulation pump flow rate to 450L / min to make the cooling rate 25℃ / s; until the temperature drops to 190℃, obtain the second gear; S9. Use the feature vector as input to the parameter prediction model to obtain the tempering temperature and tempering time. Perform isothermal tempering on the third gear according to the tempering temperature and tempering time to obtain the fourth gear. S10. The fourth gear is strengthened by a multi-energy field coupling stress relief process to obtain the fifth gear; S11. Collect the tooth profile data of the fifth gear, and perform precision machining on the fifth gear through a deformation compensation cutting strategy to obtain a high-strength and tough gear.

[0022] Example 2: S1. Select high-speed steel of type CPM 10V as the pre-selected material. The pre-selected material is subjected to two normalizing forgings to obtain a grain-refined pre-selected material. The grain-refined pre-selected material is held at 1200℃ for 210 minutes to make the microstructure become austenitic. It is then quenched in quenching oil at 85℃ to make the austenitic microstructure become martensite and granular carbides. It is then oil-cooled within 1 hour after quenching. It is then tempered three times at 750℃ to homogenize the martensite microstructure. The pre-selected material is then subjected to quenching and tempering heat treatment to obtain a material billet with a core hardness of 45HRC. S2. Perform semi-finish machining on the material blank to obtain semi-finished gear components; S3. Stabilize semi-precision machined gear components to eliminate internal stress and homogenize the structure; S4. The surface of the semi-finished gear parts to be nitrided is sandblasted to activate the material surface; S5. The semi-finished machined gear components after sandblasting are subjected to nitriding heat treatment to obtain the first gear. During nitriding heat treatment, the semi-finished machined gear components are placed in an ammonia atmosphere and heated to 550℃ for 8 hours. The ammonia decomposition rate during the heating process is 54%. The nitriding heat treatment adopts a two-stage nitriding process. The temperature of the first stage nitriding process is 570℃, and the nitrogen potential is 0.45%. The temperature of the second stage nitriding process is 600℃, and the nitrogen potential is also 0.45%. S6. Perform staged quenching treatment on the first gear. Place the first gear in a quenching furnace and raise the furnace temperature to 900℃ at a rate of 20℃ / min. Hold the temperature for 2 hours. After holding, transfer the gear to a quenching tank containing polymer quenching liquid within 40 seconds. Adjust the flow rate of the circulating pump to 800L / min to make the cooling rate 120℃ / s. When the temperature drops to 550℃, transfer the gear to a quenching tank containing water-based coolant within 35 seconds. Adjust the flow rate of the circulating pump to 500L / min to make the cooling rate 45℃ / s. Continue until the temperature drops to 210℃ to obtain the second gear. S7. Perform surface carburizing and isothermal quenching on the second gear. Place the second gear in a carburizing furnace and heat it to 970°C at a rate of 15°C / min. Hold the carburizing temperature for 5 hours, and the carbon content in the carburizing furnace is 1.2%. After the carburizing temperature is held, transfer it to an isothermal quenching furnace at 360°C within 40 seconds for isothermal salt bath treatment and hold for 2 hours. After the holding temperature is held, remove it and allow it to cool naturally to room temperature to obtain the third gear. S8. Preset the scanning range, scanning step size, and scanning speed; acquire X-ray diffraction patterns, neutron diffraction data, and eddy current signals from the surface of the third gear; extract features from the X-ray diffraction patterns, neutron diffraction data, and eddy current signals to obtain X-ray diffraction features, neutron diffraction features, and eddy current features; stitch the X-ray diffraction features, neutron diffraction features, and eddy current features to obtain a feature vector; extract the position of each diffraction peak, the intensity value corresponding to the highest point, and the half-width at half-maximum (WHM) from the X-ray diffraction pattern; calculate the peak intensity ratio of adjacent diffraction peaks; calculate the grain size using the Scherrer formula; and calculate... The residual stress corresponding to different azimuth angles is calculated, and the peak intensity ratio, grain size, and residual stress are combined as X-ray diffraction features. Methods for obtaining neutron diffraction features include: extracting the diffraction peak shifts of preset crystal planes at different depths from neutron diffraction data, calculating lattice strain, calculating internal stress according to Hooke's law, and combining lattice strain and internal stress as neutron diffraction features. Methods for obtaining eddy current features include: acquiring the current in the eddy current signal and the current corresponding to changes in phase and amplitude, calculating crack depth and crack size, and combining crack depth and crack size as eddy current features. S9. Use the feature vector as input to the parameter prediction model to obtain the tempering temperature and tempering time. Perform isothermal tempering on the third gear according to the tempering temperature and tempering time to obtain the fourth gear. S10. The fourth gear is strengthened by a multi-energy field coupling stress relief process to obtain the fifth gear; S11. Collect the tooth profile data of the fifth gear, and perform precision machining on the fifth gear through a deformation compensation cutting strategy to obtain a high-strength and tough gear.

[0023] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A heat treatment process for high-strength and tough gears, characterized in that... Includes the following steps: S1. Select high-speed steel of type CPM 10V as the pre-selected material, perform two normalizing forgings on the pre-selected material to obtain a pre-selected material with refined grains, and perform quenching and tempering heat treatment on the pre-selected material to obtain a material billet with a core hardness of 31-45HRC. S2. Perform semi-precision machining on the material blank to obtain a semi-precision machined gear component; S3. Stabilize the semi-precision machined gear components; S4. The surface of the semi-finished gear component to be nitrided is subjected to sandblasting treatment; S5. Nitriding heat treatment is performed on the semi-finished gear parts after sandblasting to obtain the first gear; S6. Perform stage quenching treatment on the first gear to obtain the second gear; S7. Perform surface carburizing and isothermal quenching on the second gear to obtain the third gear; S8. Set the scanning range, scanning step size, and scanning speed, and collect X-ray diffraction patterns, neutron diffraction data, and eddy current signals on the surface of the third gear; extract features from the X-ray diffraction patterns, neutron diffraction data, and eddy current signals to obtain X-ray diffraction features, neutron diffraction features, and eddy current features; The feature vector is obtained by splicing the X-ray diffraction features, neutron diffraction features and eddy current features; S9. Using the feature vector as input to the parameter prediction model, the tempering temperature and tempering time are obtained. The third gear is subjected to isothermal tempering treatment based on the tempering temperature and tempering time to obtain the fourth gear. S10. The fourth gear is strengthened by a multi-energy field coupling stress relief process to obtain the fifth gear; S11. Collect the tooth profile data of the fifth gear, and perform precision machining on the fifth gear through a deformation compensation cutting strategy to obtain a high-strength and tough gear.

2. The high-strength and tough gear heat treatment process according to claim 1, characterized in that, In step S1, the pre-selected material for grain refinement is held at 850-1200℃ for 150-210 min to transform the microstructure into austenitic microstructure. It is then quenched in quenching oil at 45-85℃ to transform the austenitic microstructure into martensite and granular carbides. After quenching, it is oil-cooled within 1 hour and then tempered 2-3 times at 550-750℃ to homogenize the martensite microstructure.

3. The high-strength and tough gear heat treatment process according to claim 1, characterized in that, In step S5, the nitriding heat treatment involves placing the semi-finished machined gear component in an ammonia atmosphere and heating it to 500-550℃ for 5-8 hours. During the heating process, the ammonia decomposition rate is 37-54%. The nitriding heat treatment adopts a two-stage nitriding process. The temperature of the first stage nitriding process is 530-570℃, and the nitrogen potential is 0.35%-0.45%. The temperature of the second stage nitriding process is 550-600℃, and the nitrogen potential is 0.35%-0.45%.

4. The high-strength and tough gear heat treatment process according to claim 1, characterized in that, In step S6, the first gear is placed in a quenching furnace, and the furnace temperature is raised to 900℃ at a rate of 15-20℃ / min and held for 1.5-2 hours. After the holding period, it is transferred to a quenching tank containing polymer quenching liquid within 40 seconds. The flow rate of the circulating pump is adjusted to 600-800L / min to make the cooling rate 90-120℃ / s. When the temperature drops to 500-550℃, it is transferred to a quenching tank containing water-based coolant within 35 seconds. The flow rate of the circulating pump is adjusted to 450-500L / min to make the cooling rate 25-45℃ / s until the temperature drops to 190-210℃, thus obtaining the second gear.

5. The high-strength and high-toughness gear heat treatment process according to claim 1, characterized in that, In step S7, the second gear is placed in a carburizing furnace and heated to 950-970℃ at a rate of 10-15℃ / min, and then carburized for 4-5 hours. The carbon content in the carburizing furnace is 1.0%-1.2%. After the carburizing is completed, the gear is transferred to an isothermal quenching furnace at 330-360℃ within 40 seconds for isothermal salt bath treatment and held for 2 hours. After the holding is completed, the gear is removed and allowed to cool naturally to room temperature to obtain the third gear.

6. The high-strength and tough gear heat treatment process according to claim 1, characterized in that, In step S8, the position of each diffraction peak, the intensity value corresponding to the highest point, and the full width at half maximum (FWHM) are extracted from the X-ray diffraction pattern. The peak intensity ratio of adjacent diffraction peaks is calculated, the grain size is calculated using the Scherrer formula, and the residual stress corresponding to different azimuth angles is calculated. The peak intensity ratio, grain size, and residual stress are then combined as X-ray diffraction features.