CN100392143C - Nitriding heat treatment process of high temperature alloy material - Google Patents

Abstract

The present invention discloses a nitriding heat treatment process of high temperature alloy material, which is carried out according to the following steps: (1) the temperature of a furnace provided with parts is heated to 150 DEG C+/-10 DEG C, simultaneously, ammonia air is switched on, the temperature is preserved for two hours so as to eliminate furnace air; (2) the furnace temperature is heated to 300 DEG C+/-10 DEG C, and the heat is preserved for two hours; (3) the furnace temperature is heated to 575 DEG C+/-15 DEG C at the speed of less than or equal to 50 DEG C /h, simultaneously, the ammonia dissociation rate is adjusted from 30 to 65 percent, the temperature is preserved for at least 40 hours, then, outer samples are detected, and the final end time of temperature preservation is determined; (4) after the temperature preservation is ended, the furnace temperature is heated to 650 DEG C+/-10 DEG C, simultaneously, the ammonia dissociation rate is adjusted to not less than 90 percent, and the temperature is preserved for at least 4 hours; (5) a power supply is switched off, a workpiece naturally cools down along with the furnace, simultaneously, trace ammonia air is switched on, and the positive pressure is kept in the furnace; (6), when the furnace temperature drops to less than and equal to 150 DEG C, the workpiece can be discharged from the furnace and cooled in the air. A part which is carried out by the nitriding heat treatment process of the present invention is used, the surface hardness of the part is more than 800 HV, and the wear resistance of the part is greatly improved.

Description

Nitriding heat treatment process of high temperature alloy material

(1) technical field

The present invention relates to nitriding heat treatment process of high temperature alloy material, particularly the nitriding heat treatment process of GH901 high temperature alloy.

(2) background technology

The GH901 alloy is a kind of Fe-Ni-Cr based high-temperature alloy with γ ' phase precipitation strength type, and matrix is an austenite structure, and main is main strengthening element with Al, Ti, Mo etc.Have higher intensity, oxidation-resistance, structure stability and good comprehensive performances at alloy below 650 ℃.Because of its alloying element content height; particularly Ti, Ni, Mo element have reduced the spread coefficient of nitrogen in iron; and alloying element and air effect; surface at part generates the fine and close oxide film with protectiveness; this layer oxide film hindered the infiltration of nitrogen-atoms, so nitriding thermal treatment routinely can't make its surface form attrition resistant nitrided case.

For working temperature some part in the supercritical steam turbine unit more than 560 ℃, as valve rod, not only need the good high-temperature performance but also need wear resistance, therefore need on the property heat treatment basis, to increase wear-resistant nitriding thermal treatment.And the part by the manufacturing of GH901 high temperature alloy is carried out thermo-chemical treatment according to conventional nitriding material or stainless nitriding heat treatment process, its surface can't form attrition resistant nitrided case at all.

(3) summary of the invention

The object of the present invention is to provide a kind of nitriding heat treatment process of high temperature alloy material, GH901 nitriding heat treatment process of high temperature alloy material particularly, adopt the part behind this nitriding heat treatment process, its surface hardness has improved the wear resistance of part greatly up to more than the 800HV.

The present invention is achieved in that a kind of nitriding heat treatment process of high temperature alloy material, follows these steps to carry out:

(1) the stove furnace temperature that part will be housed is heated to 150 ℃ ± 10 ℃, and logical simultaneously ammonia be incubated 2 hours with the eliminating furnace air;

(2) continue furnace temperature is heated to 300 ℃ ± 10 ℃, be incubated 2 hours;

(3) 50 ℃ speed is heated to 575 ℃ ± 15 ℃ with furnace temperature per hour to be not more than again, adjusts ammonia dissociation rate simultaneously 30～65%, and is incubated 40 hours at least, detects outer sample then, the final insulation concluding time of decision;

(4) after insulation finishes furnace temperature is heated to 650 ℃ ± 10 ℃, adjusts ammonia dissociation rate simultaneously to being not less than 90%, and be incubated 4 hours at least;

(5) cut off the electricity supply, part passes to micro-ammonia simultaneously with the stove naturally cooling, makes to keep malleation in the stove;

(6) when furnace temperature is reduced to smaller or equal to 150 ℃, the part air cooling of can coming out of the stove.

Adopt the part behind the nitriding heat treatment process of the present invention, its surface hardness has improved the wear resistance of part greatly up to more than the 800HV, satisfies working temperature in the supercritical steam turbine unit service requirements more than 560 ℃.This implementation of processes is easy to operate, easily and control, steady quality, pollution-free simultaneously.

(4) description of drawings

The invention will be further described below in conjunction with the drawings and specific embodiments.

Fig. 1 is a GH901 nitriding heat treatment process of high temperature alloy material synoptic diagram of the present invention.

(5) embodiment

Referring to Fig. 1, the part valve rod is made by the GH901 high temperature alloy, before beginning is handled in nitriding, should clean the part stem surface earlier and deoil, again valve rod is placed in the well formula resistance furnace with temperature automatically controlled and instrument recording unit, hang over dispersed arrangement on the support, and use enamel gas nitriding steamed stuffed bun and place the ammonium chloride energizer.The nitriding heat treatment process actually operating of GH901 high temperature alloy is the row step as follows:

(1) furnace temperature is heated to 150 ℃ ± 10 ℃, logical simultaneously ammonia is incubated 2 hours to get rid of furnace air;

(2) continue furnace temperature is heated to 300 ℃ ± 10 ℃, be incubated 2 hours;

(3) with 50 ℃ speed per hour furnace temperature is heated to 575 ℃ ± 15 ℃ again, adjusts ammonia dissociation rate simultaneously 32～55%, be incubated 45 hours, detect outer sample then, hardness and depth of penetration are all qualified, finish to be incubated;

(4) at last furnace temperature is heated to 650 ℃ ± 10 ℃, adjusting ammonia dissociation rate simultaneously is greater than 95%, and is incubated 4 hours;

(5) cut off the electricity supply, part passes to micro-ammonia simultaneously with the stove naturally cooling, makes to keep malleation in the stove;

(6) when furnace temperature is reduced to 150 ℃, the part air cooling of coming out of the stove.

So far the nitriding heat treatment process of GH901 high temperature alloy is finished.Through to the part valve rod after the nitriding with stove in sample detect, its microscopic test data see Table 1.

Microscopic test data after the nitrogenize of table 1 valve rod

Specimen coding	Nitride layer depth (mm)	Nitride layer hardness (HV)
			1	0.0558	806-927
2	0.0558	817-995
			3	0.0527	809-849
4	0.0527	917-995
			5	0.0558	857-965
6	0.0527	833-955

The analytical test data as seen, after nitriding was handled, the surface hardness of workpiece valve rod reached 800～1000HV, has improved the wear resistance of part greatly, the GH901 high temperature alloy satisfies working temperature in the supercritical steam turbine unit service requirements more than 560 ℃ can life-time service below 650 ℃.

Claims (1)

1. nitriding heat treatment process of high temperature alloy material is characterized in that following these steps to carrying out:

(1) the stove furnace temperature that part will be housed is heated to 150 ℃ ± 10 ℃, and logical simultaneously ammonia be incubated 2 hours with the eliminating furnace air;

(2) continue furnace temperature is heated to 300 ℃ ± 10 ℃, be incubated 2 hours;

(3) 50 ℃ speed is heated to 575 ℃ ± 15 ℃ with furnace temperature per hour to be not more than again, adjusts ammonia dissociation rate simultaneously 30～65%, and is incubated 40 hours at least, detects outer sample then, the final insulation concluding time of decision;

(4) after insulation finishes furnace temperature is heated to 650 ℃ ± 10 ℃, adjusts ammonia dissociation rate simultaneously to being not less than 90%, and be incubated 4 hours at least;

(5) cut off the electricity supply, part passes to micro-ammonia simultaneously with the stove naturally cooling, makes to keep malleation in the stove;

(6) when furnace temperature is reduced to smaller or equal to 150 ℃, the part air cooling of can coming out of the stove.

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